Method for applying reflective quality of service in wireless communication system, and device therefor

ABSTRACT

In an aspect of the present invention, a method for a user equipment (UE) to perform reflective quality of service (QoS) in a wireless communication system may include the steps of receiving a downlink packet from a network, wherein the downlink packet is a packet to which the application of the reflective QoS is indicated; deriving a QoS rule based on the downlink packet; applying a QoS marking of the downlink packet to an uplink packet using the QoS rule and transmitting the uplink packet to the network; and restarting a timer associated with the QoS rule when the downlink packet is received before the timer expires.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/KR2017/010476, filed on Sep. 22,2017, which claims the benefit of U.S. Provisional Application No.62/489,998, filed on Apr. 25, 2017, U.S. Provisional Application No.62/477,438, filed on Mar. 28, 2017, U.S. Provisional Application No.62/474,082, filed on Mar. 21, 2017, U.S. Provisional Application No.62/418,799, filed on Nov. 8, 2016, and U.S. Provisional Application No.62/406,423, filed on Oct. 11, 2016. The disclosures of the priorapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method of applying/supporting reflective QoS andan apparatus performing the same.

BACKGROUND ART

A mobile communication system has been developed to provide a voiceservice while guaranteeing activity of a user. However, the mobilecommunication system extends an area up to a data service as well as avoice and at present, a short phenomenon of a resource is caused due toan explosive increase of traffic and uses require a higher-speedservice, and as a result, a more developed mobile communication systemis required.

Requirements of a next-generation mobile communication system largelyneed to support accommodation of explosive data traffic, an epochalincrease of transmission rate per user, accommodation of thesignificantly increased number of connection devices, very lowend-to-end latency, and high energy efficiency. To this end, varioustechnologies have been researched, which include dual connectivity,massive multiple input multiple output (MIMO), in-band full duplex,non-orthogonal multiple access (NOMA), super wideband supporting, devicenetworking, and the like.

DISCLOSURE Technical Problem

An object of the present invention is to propose an efficient reflectiveQoS procedure.

Furthermore, an object of the present invention is to propose a timeroperation for counting a reflective QoS application-valid time in orderto efficiently operate a reflective QoS procedure.

Technical objects to be achieved by the present invention are notlimited to the aforementioned objects, and those skilled in the art towhich the present invention pertains may evidently understand othertechnological objects from the following description.

Technical Solution

In an aspect of the present invention, a method for a user equipment(UE) to perform reflective quality of service (QoS) in a wirelesscommunication system may include the steps of receiving a downlinkpacket from a network, wherein the downlink packet is a packet to whichthe application of the reflective QoS is indicated; deriving a QoS rulebased on the downlink packet; applying a QoS marking of the downlinkpacket to an uplink packet using the QoS rule and transmitting theuplink packet to the network; and restarting a timer associated with theQoS rule when the downlink packet is received before the timer expires.

Furthermore, the method of performing the reflective QoS may furtherinclude the step of deleting the QoS rule when the timer expires.

Furthermore, the method of performing the reflective QoS may furtherinclude the step of starting the timer when the downlink packet isreceived after the timer expires.

Furthermore, a value of the timer may be previously determined in theprotocol data unit (PDU) session establishment procedure of the UE.

Furthermore, if the network is an access network (AN), the AN may be anetwork node receiving reflective QoS indication indicative of thereflective QoS application of the downlink packet and the QoS markingthrough an encapsulation header on an N3 reference point from a userplane function.

Furthermore, the QoS marking may correspond to an identifier of a QoSflow of the downlink packet.

Furthermore, the QoS rule may be used to determine a mapping relationbetween the uplink packet and the QoS flow.

Furthermore, the QoS rule may include a packet filter derived from thedownlink packet, the QoS marking of the downlink packet, and aprecedence value used to determine the evaluation order of the uplinkpacket.

Furthermore, the packet filter may be derived from a header of thedownlink packet.

Furthermore, the step of applying the QoS marking of the downlink packetto the uplink packet using the QoS rule and transmitting the uplinkpacket to the network may include the steps of filtering an uplinkpacket matched with the packet filter included in the QoS rule byevaluating a plurality of uplink packets in the order of the precedencevalue; and applying the QoS marking included in the QoS rule to thefiltered uplink packet and transmitting the filtered uplink packet tothe network.

Furthermore, the step of deriving the QoS rule based on the downlinkpacket may include the steps of checking whether the QoS rule associatedwith the downlink packet is present; and deriving the QoS rule based onthe downlink packet if the QoS rule associated with the downlink packetis not present and starting the timer.

Furthermore, the QoS rule derived according to the reflective QoSapplication may have lower priority than an explicitly signaled QoSrule.

Furthermore, the application of the reflective QoS may be deactivatedthrough a user plane or a control plane.

Furthermore, a user equipment (UE) for performing reflective quality ofservice (QoS) in a wireless communication system according to anotherembodiment of the present invention may include a communication moduleconfigured to transmit/receive a signal; and a processor configured tocontrol the communication module, wherein the processor may receivedownlink packet from a network, the downlink packet being a packet towhich the application of the reflective QoS is indicated, may derive aQoS rule based on the downlink packet, may apply a QoS marking of thedownlink packet to an uplink packet using the QoS rule and transmit theuplink packet to the network, and may restart a timer associated withthe QoS rule when the downlink packet is received before the timerexpires.

Furthermore, the processor may delete the QoS rule when the timerexpires.

Furthermore, the QoS rule may include a packet filter derived from thedownlink packet, the QoS marking of the downlink packet, and aprecedence value used to determine the evaluation order of the uplinkpacket.

Advantageous Effects

In accordance with an embodiment of the present invention, there areeffects in that signaling overhead for QoS marking is reduced and a QoSprocedure is simplified by applying a reflective QoS.

Furthermore, in accordance with an embodiment of the present invention,there is an effect in that a burden of a UE which may occur because aunnecessary QoS rule is consistently managed/stored can be significantlyreduced because a UE deletes a reflective QoS whose timer has expired inreal time by applying a reflective QoS timer.

Furthermore, in accordance with an embodiment of the present invention,there are effects in that signaling overhead is reduced and a timeroperation procedure is simplified because a separate indicator forstarting/restarting a timer does not need to be signaled.

Technical effects of the present invention are not limited to thetechnical effects described above, and those skilled in the art mayunderstand other technical effects not mentioned herein from thefollowing description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention as a part of detailed descriptions,illustrate embodiments of the invention and together with thedescriptions, serve to explain the technical principles of theinvention.

FIG. 1 illustrates an Evolved Packet System (EPS) to which the presentinvention can be applied.

FIG. 2 illustrates one example of an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN) to which the present invention can be applied.

FIG. 3 illustrates structures of an E-UTRAN and an EPC in a wirelesscommunication system to which the present invention may be applied.

FIG. 4 illustrates a radio interface protocol structure between a UE andan E-UTRAN in a wireless communication system to which the presentinvention may be applied.

FIG. 5 is a diagram illustrating in brief the structure of a physicalchannel in a wireless communication system to which the presentinvention may be applied.

FIG. 6 is a diagram illustrating 5G system architecture using areference point representation.

FIG. 7 is a diagram illustrating 5G system architecture using aservice-based representation.

FIG. 8 illustrates NG-RAN architecture to which the present inventionmay be applied.

FIG. 9 is a diagram illustrating a radio protocol stack to which thepresent invention may be applied.

FIG. 10 illustrates RM state models to which the present invention maybe applied.

FIG. 11 illustrates CM state models to which the present invention maybe applied.

FIG. 12 illustrates classification and user plane marking for a QoS flowand the mapping of a QoS flow to AN resources according to an embodimentof the present invention.

FIG. 13 is a diagram illustrating 5G system architecture to which thepresent invention may be applied.

FIG. 14 illustrates a QoS flow mapping method for uplink traffic of a UEto which the present invention may be applied.

FIG. 15 is a flowchart illustrating a method of determining whetherreflective QoS will be used and a reflective QoS indication method in aprocess of setting up a PDU session according to an embodiment of thepresent invention.

FIG. 16 is a flowchart illustrating a reflective QoS indication methodaccording to a method 1 of the present invention.

FIG. 17 is a flowchart illustrating a reflective QoS indication methodaccording to a method 2 of the present invention.

FIG. 18 is a flowchart illustrating a method of recovering reflectiveQoS-related information if the reflective QoS-related information islost while the method 2 is applied.

FIG. 19 is a flowchart illustrating a reflective QoS procedure accordingto an embodiment of the present invention.

FIG. 20 shows a block diagram of a communication apparatus according toan embodiment of the present invention.

FIG. 21 shows a block diagram of a communication apparatus according toan embodiment of the present invention.

MODE FOR INVENTION

In what follows, preferred embodiments according to the presentinvention will be described in detail with reference to appendeddrawings. The detailed descriptions provided below together withappended drawings are intended only to explain illustrative embodimentsof the present invention, which should not be regarded as the soleembodiments of the present invention. The detailed descriptions belowinclude specific information to provide complete understanding of thepresent invention. However, those skilled in the art will be able tocomprehend that the present invention can be embodied without thespecific information.

For some cases, to avoid obscuring the technical principles of thepresent invention, structures and devices well-known to the public canbe omitted or can be illustrated in the form of block diagrams utilizingfundamental functions of the structures and the devices.

A base station in this document is regarded as a terminal node of anetwork, which performs communication directly with a UE. In thisdocument, particular operations regarded to be performed by the basestation may be performed by a upper node of the base station dependingon situations. In other words, it is apparent that in a networkconsisting of a plurality of network nodes including a base station,various operations performed for communication with a UE can beperformed by the base station or by network nodes other than the basestation. The term Base Station (BS) can be replaced with a fixedstation, Node B, evolved-NodeB (eNB), Base Transceiver System (BTS), orAccess Point (AP). Also, a terminal can be fixed or mobile; and the termcan be replaced with User Equipment (UE), Mobile Station (MS), UserTerminal (UT), Mobile Subscriber Station (MSS), Subscriber Station (SS),Advanced Mobile Station (AMS), Wireless Terminal (WT), Machine-TypeCommunication (MTC) device, Machine-to-Machine (M2M) device, orDevice-to-Device (D2D) device.

In what follows, downlink (DL) refers to communication from a basestation to a terminal, while uplink (UL) refers to communication from aterminal to a base station. In downlink transmission, a transmitter canbe part of the base station, and a receiver can be part of the terminal.Similarly, in uplink transmission, a transmitter can be part of theterminal, and a receiver can be part of the base station.

Specific terms used in the following descriptions are introduced to helpunderstanding the present invention, and the specific terms can be usedin different ways as long as it does not leave the technical scope ofthe present invention.

The technology described below can be used for various types of wirelessaccess systems based on Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Orthogonal Frequency Division Multiple Access (OFDMA), Single CarrierFrequency Division Multiple Access (SC-FDMA), or Non-Orthogonal MultipleAccess (NOMA). CDMA can be implemented by such radio technology asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented by such radio technology as Global System for Mobilecommunications (GSM), General Packet Radio Service (GPRS), or EnhancedData rates for GSM Evolution (EDGE). OFDMA can be implemented by suchradio technology as the IEEE 802.11 (Wi-Fi), the IEEE 802.16 (WiMAX),the IEEE 802-20, or Evolved UTRA (E-UTRA). UTRA is part of the UniversalMobile Telecommunications System (UMTS). The 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS(E-UMTS) which uses the E-UTRA, employing OFDMA for downlink and SC-FDMAfor uplink transmission. The LTE-A (Advanced) is an evolved version ofthe 3GPP LTE system.

Embodiments of the present invention can be supported by standarddocuments disclosed in at least one of wireless access systems includingthe IEEE 802, 3GPP, and 3GPP2 specifications. In other words, among theembodiments of the present invention, those steps or parts omitted forthe purpose of clearly describing technical principles of the presentinvention can be supported by the documents above. Also, all of theterms disclosed in this document can be explained with reference to thestandard documents.

To clarify the descriptions, this document is based on the 3GPPLTE/LTE-A, but the technical features of the present invention are notlimited to the current descriptions.

Terms used in this document are defined as follows.

-   -   Universal Mobile Telecommunication System (UMTS): the 3rd        generation mobile communication technology based on GSM,        developed by the 3GPP    -   Evolved Packet System (EPS): a network system comprising an        Evolved Packet Core (EPC), a packet switched core network based        on the Internet Protocol (IP) and an access network such as the        LTE and UTRAN. The EPS is a network evolved from the UMTS.    -   NodeB: the base station of the UMTS network. NodeB is installed        outside and provides coverage of a macro cell.    -   eNodeB: the base station of the EPS network. eNodeB is installed        outside and provides coverage of a macro cell.    -   User Equipment (UE): A UE can be called a terminal, Mobile        Equipment (ME), or Mobile Station (MS). A UE can be a portable        device such as a notebook computer, mobile phone, Personal        Digital Assistant (PDA), smart phone, or a multimedia device; or        a fixed device such as a Personal Computer (PC) or        vehicle-mounted device. The term UE may refer to an MTC terminal        in the description related to MTC.    -   IP Multimedia Subsystem (IMS): a sub-system providing multimedia        services based on the IP    -   International Mobile Subscriber Identity (IMSI): a globally        unique subscriber identifier assigned in a mobile communication        network    -   Machine Type Communication (MTC): communication performed by        machines without human intervention. It may be called        Machine-to-Machine (M2M) communication.    -   MTC terminal (MTC UE or MTC device or MRT apparatus): a terminal        (e.g., a vending machine, meter, and so on) equipped with a        communication function (e.g., communication with an MTC server        through PLMN) operating through a mobile communication network        and performing the MTC functions.    -   MTC server: a server on a network managing MTC terminals. It can        be installed inside or outside a mobile communication network.        It can provide an interface through which an MTC user can access        the server. Also, an MTC server can provide MTC-related services        to other servers (in the form of Services Capability Server        (SCS)) or the MTC server itself can be an MTC Application        Server.    -   (MTC) application: services (to which MTC is applied) (for        example, remote metering, traffic movement tracking, weather        observation sensors, and so on)    -   (MTC) Application Server: a server on a network in which (MTC)        applications are performed    -   MTC feature: a function of a network to support MTC        applications. For example, MTC monitoring is a feature intended        to prepare for loss of a device in an MTC application such as        remote metering, and low mobility is a feature intended for an        MTC application with respect to an MTC terminal such as a        vending machine.    -   MTC user: an MTC user uses a service provided by an MTC server.    -   MTC subscriber: an entity having a connection relationship with        a network operator and providing services to one or more MTC        terminals.    -   MTC group: an MTC group shares at least one or more MTC features        and denotes a group of MTC terminals belonging to MTC        subscribers.    -   Services Capability Server (SCS): an entity being connected to        the 3GPP network and used for communicating with an MTC        InterWorking Function (MTC-IWF) on a Home PLMN (HPLMN) and an        MTC terminal. The SCS provides the capability for a use by one        or more MTC applications.    -   External identifier: a globally unique identifier used by an        external entity (for example, an SCS or an Application Server)        of the 3GPP network to indicate (or identify) an MTC terminal        (or a subscriber to which the MTC terminal belongs). An external        identifier comprises a domain identifier and a local identifier        as described below.    -   Domain identifier: an identifier used for identifying a domain        in the control region of a mobile communication network service        provider. A service provider can use a separate domain        identifier for each service to provide an access to a different        service.    -   Local identifier: an identifier used for deriving or obtaining        an International Mobile Subscriber Identity (IMSI). A local        identifier should be unique within an application domain and is        managed by a mobile communication network service provider.    -   Radio Access Network (RAN): a unit including a Node B, a Radio        Network Controller (RNC) controlling the Node B, and an eNodeB        in the 3GPP network. The RAN is defined at the terminal level        and provides a connection to a core network.    -   Home Location Register (HLR)/Home Subscriber Server (HSS): a        database provisioning subscriber information within the 3GPP        network. An HSS can perform functions of configuration storage,        identity management, user state storage, and so on.    -   RAN Application Part (RANAP): an interface between the RAN and a        node in charge of controlling a core network (in other words, a        Mobility Management Entity (MME)/Serving GPRS (General Packet        Radio Service) Supporting Node (SGSN)/Mobile Switching Center        (MSC)).    -   Public Land Mobile Network (PLMN): a network formed to provide        mobile communication services to individuals. The PLMN can be        formed separately for each operator.    -   Non-Access Stratum (NAS): a functional layer for exchanging        signals and traffic messages between a terminal and a core        network at the UMTS and EPS protocol stack. The NAS is used        primarily for supporting mobility of a terminal and a session        management procedure for establishing and maintaining an IP        connection between the terminal and a PDN GW.    -   Service Capability Exposure Function (SCEF): an entity in 3GPP        architecture for the service capability exposure that provides a        means for safely exposing a service and a capability provided by        3GPP network interface.

In what follows, the present invention will be described based on theterms defined above.

Overview of System to which the Present Invention can be Applied

FIG. 1 illustrates an Evolved Packet System (EPS) to which the presentinvention can be applied.

The network structure of FIG. 1 is a simplified diagram restructuredfrom an Evolved Packet System (EPS) including Evolved Packet Core (EPC).

The EPC is a main component of the System Architecture Evolution (SAE)intended for improving performance of the 3GPP technologies. SAE is aresearch project for determining a network structure supporting mobilitybetween multiple heterogeneous networks. For example, SAE is intended toprovide an optimized packet-based system which supports various IP-basedwireless access technologies, provides much more improved datatransmission capability, and so on.

More specifically, the EPC is the core network of an IP-based mobilecommunication system for the 3GPP LTE system and capable of supportingpacket-based real-time and non-real time services. In the existingmobile communication systems (namely, in the 2nd or 3rd mobilecommunication system), functions of the core network have beenimplemented through two separate sub-domains: a Circuit-Switched (CS)sub-domain for voice and a Packet-Switched (PS) sub-domain for data.However, in the 3GPP LTE system, an evolution from the 3rd mobilecommunication system, the CS and PS sub-domains have been unified into asingle IP domain. In other words, in the 3GPP LTE system, connectionbetween UEs having IP capabilities can be established through anIP-based base station (for example, eNodeB), EPC, and application domain(for example, IMS). In other words, the EPC provides the architectureessential for implementing end-to-end IP services.

The EPC comprises various components, where FIG. 1 illustrates part ofthe EPC components, including a Serving Gateway (SGW or S-GW), PacketData Network Gateway (PDN GW or PGW or P-GW), Mobility Management Entity(MME), Serving GPRS Supporting Node (SGSN), and enhanced Packet DataGateway (ePDG).

The SGW operates as a boundary point between the Radio Access Network(RAN) and the core network and maintains a data path between the eNodeBand the PDN GW. Also, in case the UE moves across serving areas by theeNodeB, the SGW acts as an anchor point for local mobility. In otherwords, packets can be routed through the SGW to ensure mobility withinthe E-UTRAN (Evolved-UMTS (Universal Mobile Telecommunications System)Terrestrial Radio Access Network defined for the subsequent versions ofthe 3GPP release 8). Also, the SGW may act as an anchor point formobility between the E-UTRAN and other 3GPP networks (the RAN definedbefore the 3GPP release 8, for example, UTRAN or GERAN (GSM (GlobalSystem for Mobile Communication)/EDGE (Enhanced Data rates for GlobalEvolution) Radio Access Network).

The PDN GW corresponds to a termination point of a data interface to apacket data network. The PDN GW can support policy enforcement features,packet filtering, charging support, and so on. Also, the PDN GW can actas an anchor point for mobility management between the 3GPP network andnon-3GPP networks (for example, an unreliable network such as theInterworking Wireless Local Area Network (I-WLAN) or reliable networkssuch as the Code Division Multiple Access (CDMA) network and Wimax).

In the example of a network structure as shown in FIG. 1, the SGW andthe PDN GW are treated as separate gateways; however, the two gatewayscan be implemented according to single gateway configuration option.

The MME performs signaling for the UE's access to the network,supporting allocation, tracking, paging, roaming, handover of networkresources, and so on; and control functions. The MME controls controlplane functions related to subscribers and session management. The MMEmanages a plurality of eNodeBs and performs signaling of theconventional gateway's selection for handover to other 2G/3G networks.Also, the MME performs such functions as security procedures,terminal-to-network session handling, idle terminal location management,and so on.

The SGSN deals with all kinds of packet data including the packet datafor mobility management and authentication of the user with respect toother 3GPP networks (for example, the GPRS network).

The ePDG acts as a security node with respect to an unreliable, non-3GPPnetwork (for example, I-WLAN, WiFi hotspot, and so on).

As described with respect to FIG. 1, a UE with the IP capability canaccess the IP service network (for example, the IMS) that a serviceprovider (namely, an operator) provides, via various components withinthe EPC based not only on the 3GPP access but also on the non-3GPPaccess.

Also, FIG. 1 illustrates various reference points (for example, S1-U,S1-MME, and so on). The 3GPP system defines a reference point as aconceptual link which connects two functions defined in disparatefunctional entities of the E-UTAN and the EPC. Table 1 below summarizesreference points shown in FIG. 1. In addition to the examples of FIG. 1,various other reference points can be defined according to networkstructures.

TABLE 1 Reference point Description S1-MME Reference point for thecontrol plane protocol between E-UTRAN and MME S1-U Reference pointbetween E-UTRAN and Serving GW for the per bearer user plane tunnelingand inter eNodeB path switching during handover S3 It enables user andbearer information exchange for inter 3GPP access network mobility inidle and/or active state. This reference point can be used intra-PLMN orinter- PLMN (e.g. in the case of lnter-PLMN HO). S4 It provides relatedcontrol and mobility support between GPRS core and the 3GPP anchorfunction of Serving GW. In addition, if direct tunnel is notestablished, it provides the user plane tunneling. S5 It provides userplane tunneling and tunnel management between Serving GW and PDN GW. Itis used for Serving GW relocation due to UE mobility if the Serving GWneeds to connect to a non-collocated PDN GW for the required PDNconnectivity. S11 Reference point for the control plane protocol betweenMME and SGW SGi It is the reference point between the PDN GW and thepacket data network. Packet data network may be an operator externalpublic or private packet data network or an intra-operator packet datanetwork (e.g., for provision of IMS services). This reference pointcorresponds to Gi for 3GPP accesses.

Among the reference points shown in FIG. 1, S2a and S2b corresponds tonon-3GPP interfaces. S2a is a reference point which provides reliable,non-3GPP access, related control between PDN GWs, and mobility resourcesto the user plane. S2b is a reference point which provides relatedcontrol and mobility resources to the user plane between ePDG and PDNGW.

FIG. 2 illustrates one example of an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN) to which the present invention can be applied.

The E-UTRAN system has evolved from an existing UTRAN system and may bethe 3GPP LTE/LTE-A system, for example. A communication system isdisposed over a wide area to provide various communication servicesincluding voice communication through IMS and packet data (for example,VoIP (Voice over Internet Protocol)).

Referring to FIG. 2, an E-UMTS network comprises an E-UTRAN, EPC, andone or more UEs. The E-UTRAN comprises eNBs providing a UE with acontrol plane and user plane protocols, where the eNBs are connected toeach other through X2 interface.

The X2 user plane interface (X2-U) is defined among the eNBs. The X2-Uinterface provides non-guaranteed delivery of the user plane ProtocolData Unit (PDU).

The X2 control plane interface (X2-CP) is defined between twoneighboring eNBs. The X2-CP performs the functions of context deliverybetween eNBs, control of user plane tunnel between a source eNB and atarget eNB, delivery of handover-related messages, uplink loadmanagement, and so on.

The eNB is connected to the UE through a radio interface and isconnected to the Evolved Packet Core (EPC) through the S1 interface.

The S1 user plane interface (S1-U) is defined between the eNB and theServing Gateway (S-GW). The S1 control plane interface (S1-MME) isdefined between the eNB and the Mobility Management Entity (MME). The S1interface performs the functions of EPS bearer service management, NASsignaling transport, network sharing, MME load balancing management, andso on. The S1 interface supports many-to-many-relation between the eNBand the MME/S-GW.

An MME is capable of performing various functions such as NAS signalingsecurity, AS (Access Stratum) security control, inter-CN (Core Network)signaling for supporting mobility among 3GPP access networks, IDLE modeUE reachability (including performing and controlling retransmission ofa paging message), TAI (Tracking Area Identity) management (for IDLE andactive mode UEs), PDN GW and SGW selection, MME selection for handoverin which MMEs are changed, SGSN selection for handover to a 2G or 3G3GPP access network, roaming, authentication, bearer management functionincluding dedicated bearer establishment, and support for transmissionof a PWS (Public Warning System) (including Earthquake and TsunamiWarning System (ETWS) and Commercial Mobile Alert System (CMAS))message.

FIG. 3 illustrates structures of an E-UTRAN and an EPC in a wirelesscommunication system to which the present invention may be applied.

Referring to FIG. 3, an eNB is capable of performing functions such asselection of a gateway (for example, MME), routing to a gateway duringRRC (Radio Resource Control) activation, scheduling and transmission ofa BCH (Broadcast Channel), dynamic resource allocation for a UE inuplink and downlink transmission, and mobility control connection in anLTE_ACTIVE state. As described above, a gateway belonging to an EPC iscapable of performing functions such as paging origination, LTE_IDLEstate management, ciphering of a user plane, SAE (System ArchitectureEvolution) bearer control, and ciphering of NAS signaling and integrityprotection.

FIG. 4 illustrates a radio interface protocol structure between a UE andan E-UTRAN in a wireless communication system to which the presentinvention can be applied.

FIG. 4(a) illustrates a radio protocol structure for the control plane,and FIG. 4(b) illustrates a radio protocol structure for the user plane.

With reference to FIG. 4, layers of the radio interface protocol betweenthe UE and the E-UTRAN can be divided into a first layer (L1), a secondlayer (L2), and a third layer (L3) based on the lower three layers ofthe Open System Interconnection (OSI) model, widely known in thetechnical field of communication systems. The radio interface protocolbetween the UE and the E-UTRAN consists of the physical layer, data linklayer, and network layer in the horizontal direction, while in thevertical direction, the radio interface protocol consists of the userplane, which is a protocol stack for delivery of data information, andthe control plane, which is a protocol stack for delivery of controlsignals.

The control plane acts as a path through which control messages used forthe UE and the network to manage calls are transmitted. The user planerefers to the path through which the data generated in the applicationlayer, for example, voice data, Internet packet data, and so on aretransmitted. In what follows, described will be each layer of thecontrol and the user plane of the radio protocol.

The physical layer (PHY), which is the first layer (L1), providesinformation transfer service to upper layers by using a physicalchannel. The physical layer is connected to the Medium Access Control(MAC) layer located at the upper level through a transport channelthrough which data are transmitted between the MAC layer and thephysical layer. Transport channels are classified according to how andwith which features data are transmitted through the radio interface.And data are transmitted through the physical channel between differentphysical layers and between the physical layer of a transmitter and thephysical layer of a receiver. The physical layer is modulated accordingto the Orthogonal Frequency Division Multiplexing (OFDM) scheme andemploys time and frequency as radio resources.

A few physical control channels are used in the physical layer. ThePhysical Downlink Control Channel (PDCCH) informs the UE of resourceallocation of the Paging Channel (PCH) and the Downlink Shared Channel(DL-SCH); and Hybrid Automatic Repeat reQuest (HARQ) information relatedto the Uplink Shared Channel (UL-SCH). Also, the PDCCH can carry a ULgrant used for informing the UE of resource allocation of uplinktransmission. The Physical Control Format Indicator Channel (PCFICH)informs the UE of the number of OFDM symbols used by PDCCHs and istransmitted at each subframe. The Physical HARQ Indicator Channel(PHICH) carries a HARQ ACK (ACKnowledge)/NACK (Non-ACKnowledge) signalin response to uplink transmission. The Physical Uplink Control Channel(PUCCH) carries uplink control information such as HARQ ACK/NACK withrespect to downlink transmission, scheduling request, Channel QualityIndicator (CQI), and so on. The Physical Uplink Shared Channel (PUSCH)carries the UL-SCH.

The MAC layer of the second layer (L2) provides a service to the RadioLink Control (RLC) layer, which is an upper layer thereof, through alogical channel. Also, the MAC layer provides a function of mappingbetween a logical channel and a transport channel; andmultiplexing/demultiplexing a MAC Service Data Unit (SDU) belonging tothe logical channel to the transport block, which is provided to aphysical channel on the transport channel.

The RLC layer of the second layer (L2) supports reliable datatransmission. The function of the RLC layer includes concatenation,segmentation, reassembly of the RLC SDU, and so on. To satisfy varyingQuality of Service (QoS) requested by a Radio Bearer (RB), the RLC layerprovides three operation modes: Transparent Mode (TM), UnacknowledgedMode (UM), and Acknowledge Mode (AM). The AM RLC provides errorcorrection through Automatic Repeat reQuest (ARQ). Meanwhile, in casethe MAC layer performs the RLC function, the RLC layer can beincorporated into the MAC layer as a functional block.

The Packet Data Convergence Protocol (PDCP) layer of the second layer(L2) performs the function of delivering, header compression, cipheringof user data in the user plane, and so on. Header compression refers tothe function of reducing the size of the Internet Protocol (IP) packetheader which is relatively large and includes unnecessary control toefficiently transmit IP packets such as the IPv4 (Internet Protocolversion 4) or IPv6 (Internet Protocol version 6) packets through a radiointerface with narrow bandwidth. The function of the PDCP layer in thecontrol plane includes delivering control plane data andciphering/integrity protection.

The Radio Resource Control (RRC) layer in the lowest part of the thirdlayer (L3) is defined only in the control plane. The RRC layer performsthe role of controlling radio resources between the UE and the network.To this purpose, the UE and the network exchange RRC messages throughthe RRC layer. The RRC layer controls a logical channel, transportchannel, and physical channel with respect to configuration,re-configuration, and release of radio bearers. A radio bearer refers toa logical path that the second layer (L2) provides for data transmissionbetween the UE and the network. Configuring a radio bearer indicatesthat characteristics of a radio protocol layer and channel are definedto provide specific services; and each individual parameter andoperating methods thereof are determined. Radio bearers can be dividedinto Signaling Radio Bearers (SRBs) and Data RBs (DRBs). An SRB is usedas a path for transmitting an RRC message in the control plane, while aDRB is used as a path for transmitting user data in the user plane.

The Non-Access Stratum (NAS) layer in the upper of the RRC layerperforms the function of session management, mobility management, and soon.

A cell constituting the base station is set to one of 1.25, 2.5, 5, 10,and 20 MHz bandwidth, providing downlink or uplink transmission servicesto a plurality of UEs. Different cells can be set to differentbandwidths.

Downlink transport channels transmitting data from a network to a UEinclude a Broadcast Channel (BCH) transmitting system information, PCHtransmitting paging messages, DL-SCH transmitting user traffic orcontrol messages, and so on. Traffic or a control message of a downlinkmulti-cast or broadcast service can be transmitted through the DL-SCH orthrough a separate downlink Multicast Channel (MCH). Meanwhile, uplinktransport channels transmitting data from a UE to a network include aRandom Access Channel (RACH) transmitting the initial control messageand a Uplink Shared Channel (UL-SCH) transmitting user traffic orcontrol messages.

A logical channel lies above a transmission channel and is mapped to thetransmission channel. The logical channel may be divided into a controlchannel for delivering control area information and a traffic channelfor delivering user area information. The control channel may include aBCCH (Broadcast Control Channel), PCCH (Paging Control Channel), CCCH(Common Control Channel), DCCH (Dedicated Control Channel), and MCCH(Multicast Control Channel). The traffic channel may include a DTCH(Dedicated Traffic Channel) and MTCH (Multicast Traffic Channel). ThePCCH is a downlink channel for delivering paging information and is usedwhen a network does not know the cell to which a UE belongs. The CCCH isused by a UE that does not have an RRC connection to a network. The MCCHis a point-to-multipoint downlink channel used for delivering MBMS(Multimedia Broadcast and Multicast Service) control information from anetwork to a UE. The DCCH is a point-to-point bi-directional channelused by a UE with an RRC connection delivering dedicated controlinformation between a UE and a network. The DTCH is a point-to-pointchannel dedicated to one UE for delivering user information that mayexist in an uplink and downlink. The MTCH is a point-to-multipointdownlink channel for delivering traffic data from a network to a UE.

In the case of an uplink connection between a logical channel and atransport channel, the DCCH may be mapped to a UL-SCH, and the DTCH maybe mapped to a UL-SCH, and the CCCH may be mapped to a UL-SCH. In thecase of a downlink connection between a logical channel and a transportchannel, the BCCH may be mapped to a BCH or DL-SCH, the PCCH may bemapped to a PCH, the DCCH may be mapped to a DL-SCH, the DTCH may bemapped to a DL-SCH, the MCCH may be mapped to an MCH, and the MTCH maybe mapped to the MCH.

FIG. 5 is a diagram illustrating in brief the structure of a physicalchannel in a wireless communication system to which the presentinvention may be applied.

Referring to FIG. 5, a physical channel transfers signaling and datathrough radio resources including one or more subcarriers in a frequencydomain and one or more symbols in a time domain.

One subframe having a length of 1.0 ms includes a plurality of symbols.A specific symbol(s) of the subframe (e.g., the first symbol of thesubframe) may be used for a PDCCH. The PDCCH carries information (e.g.,a resource block and modulation and coding scheme (MCS) and so on) aboutdynamically allocated resources.

New Generation Radio Access Network (NG-RAN) (or RAN) System

Terms used in a new generation radio access network may be defined asfollows.

-   -   Evolved packet system (EPS): a network system including an        evolved packet core (EPC), that is, an Internet protocol        (IP)-based packet switched core network, and an access to        network such as LTE or UTRAN. A network is an evolved network        form of universal mobile telecommunications system (UMTS).    -   eNodeB: an eNB of an EPS network. It is disposed outdoors and        has coverage of a macro cell volume.    -   International Mobile Subscriber Identity (IMSI): a user identity        internationally uniquely allocated in a mobile communication        network.    -   Public Land Mobile Network (PLMN): a network configured to        provide persons with a mobile communication service. It may be        differently configured for each operator.    -   5G system (5GS): a system including a 5G access network (AN), a        5G core network and a user equipment (UE).    -   5G access network (5G-AN) (or AN): an access network including a        new generation radio access network (NG-RAN) and/or a non-3GPP        access network (non-3GPP AN) connected to a 5G core network.    -   New generation radio access network (NG-RAN) (or RAN): a radio        access network having a common characteristic in that it is        connected to 5GC and supporting one or more of the following        options:

1) Standalone new radio.

2) New radio, that is, an anchor supporting an E-UTRA extension.

3) Standalone E-UTRA (e.g., eNodeB).

4) Anchor supporting a new radio extension

-   -   5G core network (5GC): a core network connected to a 5G access        network    -   Network function (NF): it means a processing function adopted in        3GPP within a network or defined in 3GPP. The processing        function includes a defined functional behavior and an interface        defined in 3GPP.    -   NF service: it is a (consumed) function exposed by an NF through        a service-based interface and used by another authenticated        NF(s).    -   Network slice: a logical network providing a specific network        capability(s) and network characteristic(s).    -   Network slice instance: a set of NF instance(s) forming a        network slice and required resource(s) (e.g., calculation,        storage and networking resources)    -   Protocol data unit (PDU) connectivity service: a service        providing the exchange of PDU(s) between a UE and a data        network.    -   PDU session: an association providing PDU connectivity service        between a UE and a data network. An association type may be an        Internet protocol (IP) or Ethernet or may be unstructured.    -   Non-access stratum (NAS): a functional layer for exchanging        signaling or traffic messages between a UE and a core network in        an EPS, 5GS protocol stack. It has a main function of supporting        the mobility of a UE and supporting a session management        procedure.

5G System Architecture to which the Present Invention May be Applied

A 5G system is a technology advanced from the 4th generation LTE mobilecommunication technology and a new radio access technology (RAT) throughthe evolution of the existing mobile communication network structure ora clean-state structure and an extended technology of long termevolution (LTE), and it supports extended LTE (eLTE), non-3GPP (e.g.,WLAN) access and so on.

A 5G system is defined based on a service, and an interaction betweennetwork functions (NFs) within architecture for a 5G system may beexpressed by two methods as follows.

-   -   Reference point representation (FIG. 6): indicates an        interaction between NF services within NFs described by a        point-to-point reference point (e.g., N11) between two NFs        (e.g., AMF and SMF).    -   Service-based representation (FIG. 7): network functions (e.g.,        AMFs) within a control plane (CP) permit other authenticated        network functions to access its own service. If this        representation is necessary, it also includes a point-to-point        reference point.

FIG. 6 is a diagram illustrating 5G system architecture using areference point representation.

Referring to FIG. 6, the 5G system architecture may include variouselements (i.e., a network function (NF)). This drawing illustrates anauthentication server function (AUSF), a (core) access and mobilitymanagement function (AMF), a session management function (SMF), a policycontrol function (PCF), an application function (AF), united datamanagement (UDM), a data network (DN), a user plane function (UPF), a(radio) access network ((R)AN) and a user equipment (UE) correspondingto some of the various elements.

Each of the NFs supports the following functions.

-   -   AUSF stores data for the authentication of a UE.    -   AMF provides a function for access of a UE unit and mobility        management and may be basically connected to one AMF per one UE.

Specifically, the AMF supports functions, such as signaling between CNnodes for mobility between 3GPP access networks, the termination of aradio access network (RAN) CP interface (i.e., N2 interface), thetermination (N1) of NAS signaling, NAS signaling security (NAS cipheringand integrity protection), AS security control, registration areamanagement, connection management, idle mode UE reachability (includingcontrol and execution of paging retransmission), mobility managementcontrol (subscription and policy), intra-system mobility andinter-system mobility support, the support of network slicing, SMFselection, lawful interception (for an AMF event and an interface to anLI system), the provision of transfer of a session management (SM)message between a UE and an SMF, a transparent proxy for SM messagerouting, access authentication, access authorization including a roamingright check, the provision of transfer of an SMS message between a UEand an SMSF, a security anchor function (SEA) and/or security contextmanagement (SCM).

Some or all of the functions of the AMF may be supported within a singleinstance of one AMF.

-   -   DN means an operator service, Internet access or a 3rd party        service, for example. The DN transmits a downlink protocol data        unit (PDU) to an UPF or receives a PDU, transmitted by a UE,        from a UPF.    -   PCF provides a function for receiving information about a packet        flow from an application server and determining a policy, such        as mobility management and session management. Specifically, the        PCF supports functions, such as the support of a unified policy        framework for controlling a network behavior, the provision of a        policy rule so that a CP function(s) (e.g., AMF or SMF) can        execute a policy rule, and the implementation of a front end for        accessing related subscription information in order to determine        a policy within user data repository (UDR).    -   SMF provides a session management function and may be managed by        a different SMF for each session if a UE has a plurality of        sessions.

Specifically, the SMF supports functions, such as session management(e.g., session setup, modification and release including the maintenanceof a tunnel between a UPF and an AN node), UE IP address allocation andmanagement (optionally including authentication), the selection andcontrol of the UP function, a traffic steering configuration for routingtraffic from the UPF to a proper destination, the termination of aninterface toward policy control functions, the execution of the controlpart of a policy and QoS, lawful interception (for an SM event and aninterface to an LI system), the termination of the SM part of an NASmessage, downlink data notification, the initiator of AN-specific SMinformation (transferred to an AN through N2 via the AMF), thedetermination of an SSC mode of a session, and a roaming function.

Some or all of the functions of the SMF may be supported within a singleinstance of one SMF.

-   -   UDM stores the subscription data of a user, policy data, etc.        UDM includes two parts, that is, an application front end (FE)        and user data repository (UDR).

The FE includes a UDM FE responsible for the processing of locationmanagement, subscription management and credential and a PCF responsiblefor policy control. The UDR stores data required for functions providedby the UDM-FE and a policy profile required by the PCF. Data storedwithin the UDR includes user subscription data, including a subscriptionID, security credential, access and mobility-related subscription dataand session-related subscription data, and policy data. The UDM-FEsupports functions, such as access to subscription information stored inthe UDR, authentication credential processing, user identificationhandling, access authentication, registration/mobility management,subscription management, and SMS management.

-   -   UPF transfers a downlink PDU, received from a DN, to a UE via an        (R)AN and transfers an uplink PDU, received from a UE, to a DN        via an (R)AN.

Specifically, the UPF supports functions, such as an anchor point forintra/inter RAT mobility, the external PDU session point ofinterconnection to a data network, packet routing and forwarding, a userplane part for the execution of packet inspection and a policy rule,lawful interception, a traffic usage report, an uplink classifier forsupporting the routing of traffic flow of a data network, a branchingpoint for supporting a multi-home PDU session, QoS handling (e.g., theexecution of packet filtering, gating and an uplink/downlink rate) for auser plane, uplink traffic verification (SDF mapping between a servicedata flow (SDF) and a QoS flow), transport level packet marking withinthe uplink and downlink, downlink packet buffering, and a downlink datanotification triggering function. Some or all of the functions of theUPF may be supported within a single instance of one UPF.

-   -   AF interoperates with a 3GPP core network in order to provide        services (e.g., support functions, such as an application        influence on traffic routing, network capability exposure        access, an interaction with a policy framework for policy        control).    -   (R)AN collectively refers to a new radio access network        supporting all of evolved E-UTRA (E-UTRA) and new radio (NR)        access technologies (e.g., gNB), that is, an advanced version of        the 4G radio access technology.

The gNB supports functions for radio resource management (i.e., radiobearer control and radio admission control), connection mobilitycontrol, the dynamic allocation (i.e., scheduling) of resources to a UEin the uplink/downlink, Internet protocol (IP) header compression, theencryption and integrity protection of a user data stream, the selectionof an AMF upon attachment of a UE if routing to the AMF has not beendetermined based on information provided to the UE, the selection of anAMF upon attachment of a UE, user plane data routing to an UPF(s),control plane information routing to an AMF, connection setup andrelease, the scheduling and transmission of a paging message (generatedfrom an AMF), the scheduling and transmission of system broadcastinformation (generated from an AMF or operation and maintenance (O&M)),a measurement and measurement report configuration for mobility andscheduling, transport level packet marking in the uplink, sessionmanagement, the support of network slicing, QoS flow management andmapping to a data radio bearer, the support of a UE that is an inactivemode, the distribution function of an NAS message, an NAS node selectionfunction, radio access network sharing, dual connectivity, and tightinterworking between an NR and an E-UTRA.

-   -   UE means a user device. A user apparatus may be called a term,        such as a terminal, a mobile equipment (ME) or a mobile station        (MS). Furthermore, the user apparatus may be a portable device,        such as a notebook, a mobile phone, a personal digital assistant        (PDA), a smartphone or a multimedia device, or may be a device        that cannot be carried, such as a personal computer (PC) or a        vehicle-mounted device.

In the drawings, for the clarity of description, an unstructured datastorage network function (UDSF), a structured data storage networkfunction (SDSF), a network exposure function (NEF) and an NF repositoryfunction (NRF) are not shown, but all of the NFs shown in this drawingmay perform mutual operations along with the UDSF, NEF and NRF, ifnecessary.

-   -   NEF provides means for safely exposing services and capabilities        provided by 3GPP network functions, for example, for a 3rd        party, internal exposure/re-exposure, an application function,        and edge computing. The NEF receives information from other        network function(s) (based on the exposed capability(s) of other        network function(s)). The NEF may store information received as        structured data using a standardized interface as a data storage        network function. The stored information is re-exposed to other        network function(s) and application function(s) by the NEF and        may be used for other purposes, such as analysis.    -   NRF supports a service discovery function. It receives an NF        discovery request from an NF instance and provides information        of a discovered NF instance to an NF instance. Furthermore, it        maintains available NF instances and services supported by the        available NF instances.    -   SDSF is an optional function for supporting a function of        storing and retrieving information as structured data by any        NEF.    -   UDSF is an optional function for supporting a function of        storing and retrieving information as unstructured data by any        NF.

Meanwhile, this drawing illustrates a reference model if a UE accessesone DN using one PDU session, for convenience of description, but thepresent invention is not limited thereto.

A UE may access two (i.e., local and central) data networks at the sametime using multiple PDU sessions. In this case, for different PDUsessions, two SMFs may be selected. In this case, each SMF may have theability to control both a local UPF and central UPF within a PDUsession.

Furthermore, a UE may access two (i.e., local and central) data networksprovided within one PDU session at the same time.

In the 3GPP system, a conceptual link that connects NFs within the 5Gsystem is defined as a reference point. The following illustratesreference points included in 5G system architecture represented in thisdrawing.

-   -   N1: a reference point between a UE and an AMF    -   N2: a reference point between an (R)AN and an AMF    -   N3: a reference point between an (R)AN and a UPF    -   N4: a reference point between an SMF and a UPF    -   N5: a reference point between a PCF and an AF    -   N6: a reference point between a UPF and a data network    -   N7: a reference point between an SMF and a PCF    -   N24: a reference point between a PCF within a visited network        and a PCF within a home network    -   N8: a reference point between a UDM and an AMF    -   N9: a reference point between two core UPFs    -   N10: a reference point between a UDM and an SMF    -   N11: a reference point between an AMF and an SMF    -   N12: a reference point between an AMF and an AUSF    -   N13: a reference point between a UDM and an authentication        server function (AUSF)    -   N14: a reference point between two AMFs    -   N15: a reference point between a PCF and an AMF in the case of a        non-roam ing scenario and a reference point between a PCF within        a visited network and an AMF in the case of a roaming scenario    -   N16: a reference point between two SMFs (in the case of a        roaming scenario, a reference point between an SMF within a        visited network and an SMF within a home network)    -   N17: a reference point between an AMF and an EIR    -   N18: a reference point between any NF and an UDSF    -   N19: a reference point between an NEF and an SDSF

FIG. 7 is a diagram illustrating 5G system architecture using aservice-based representation.

A service-based interface illustrated in this drawing shows a set ofservices provided/exposed by a specific NF. The service-based interfaceis used within a control plane. The following illustrates service-basedinterfaces included in the 5G system architecture represented as in thisdrawing.

-   -   Namf: a service-based interface exhibited by an AMF    -   Nsmf: a service-based interface exhibited by an SMF    -   Nnef: a service-based interface exhibited by an NEF    -   Npcf: a service-based interface exhibited by a PCF    -   Nudm: a service-based interface exhibited by a UDM    -   Naf: a service-based interface exhibited by an AF    -   Nnrf: a service-based interface exhibited by an NRF    -   Nausf: a service-based interface exhibited by an AUSF

NF service is a kind of capability exposed to another NF (i.e., NFservice consumer) by an NF (i.e., NF service supplier) through aservice-based interface. The NF may expose one or more NF service(s). Inorder to define NF service, the following criteria are applied:

-   -   NF services are derived from an information flow for describing        an end-to-end function.    -   A complete end-to-end message flow is described by the sequence        of NF service invocation.    -   Two operations for NF(s) to provide their services through        service-based interfaces are as follows:

i) “Request-response”: a control plane NF_B (i.e., NF service supplier)receives a request to provide a specific NF service (including theexecution of an operation and/or the provision of information) fromanother control plane NF_A (i.e., NF service consumer). NF_B sends NFservice results based on information provided by NF_A within a requestas a response.

In order to satisfy a request, NF_B may alternately consume NF servicesfrom other NF(s). In the request-response mechanism, communication isperformed in a one-to-one manner between two NFs (i.e., consumer andsupplier).

ii) “subscribe-notify”

A control plane NF_A (i.e., NF service consumer) subscribes to an NFservice provided by another control plane NF_B (i.e., NF servicesupplier). A plurality of control plane NF(s) may subscribe to the samecontrol plane NF service. NF_B notifies interested NF(s) that havesubscribed to NF services of the results of the NF services. Asubscription request from a consumer may include a notification requestfor notification triggered through periodical update or a specific event(e.g., the change, specific threshold arrival, etc. of requestedinformation). The mechanism also includes a case where NF(s) (e.g.,NF_B) implicitly subscribe to specific notification without an explicitsubscription request (e.g., due to a successful registration procedure).

FIG. 8 illustrates NG-RAN architecture to which the present inventionmay be applied.

Referring to FIG. 8, a new generation radio access network (NG-RAN)includes an NR NodeB (gNB)(s) and/or an eNodeB (eNB)(s) for providingthe termination of a user plane and control plane protocol toward a UE.

An Xn interface is connected between gNBs and between a gNB(s) and aneNB(s) connected to 5GC. The gNB(s) and the eNB(s) are also connected to5GC using an NG interface. More specifically, the gNB(s) and eNB(s) arealso connected to an AMF using an NG-C interface (i.e., N2 referencepoint), that is, a control plane interface between an NG-RAN and 5GC andare connected to a UPF using an NG-U interface (i.e., N3 referencepoint), that is, a user plane interface between an NG-RAN and 5GC.

Radio Protocol Architecture

FIG. 9 is a diagram illustrating a radio protocol stack to which thepresent invention may be applied. Specifically, FIG. 9(a) illustrates aradio interface user plane protocol stack between a UE and a gNB, andFIG. 9(b) illustrates a radio interface control plane protocol stackbetween the UE and the gNB.

A control plane means a passage through which control messages aretransmitted in order for a UE and a network to manage a call. A userplane means a passage through which data generated in an applicationlayer, for example, voice data or Internet packet data is transmitted.

Referring to FIG. 9(a), the user plane protocol stack may be dividedinto a first layer (Layer 1) (i.e., a physical layer (PHY) layer) and asecond layer (Layer 2).

Referring to FIG. 9(b), the control plane protocol stack may be dividedinto a first layer (i.e., a PHY layer), a second layer, a third layer(i.e., a radio resource control (RRC) layer) and a non-access stratum(NAS) layer.

The second layer is divided into a medium access control (MAC) sublayer,a radio link control (RLC) sublayer, a packet data convergence protocol(PDC) sublayer, and a service data adaptation protocol (SDAP) sublayer(in the case of a user plane).

Radio bearers are classified into two groups: a data radio bearer (DRB)for user plane data and a signaling radio bearer (SRB) for control planedata

Hereinafter, the layers of the control plane and user plane of the radioprotocol are described.

1) The PHY layer, that is, the first layer, provides informationtransfer service to a higher layer using a physical channel. The PHYlayer is connected to the MAC sublayer located in a high level through atransport channel. Data is transmitted between the MAC sublayer and thePHY layer through a transport channel. The transport channel isclassified depending on how data is transmitted according to whichcharacteristics through a radio interface. Furthermore, data istransmitted between different physical layers, that is, between the PHYlayer of a transmission stage and the PHY layer of a reception stagethrough a physical channel.

2) The MAC sublayer performs mapping between a logical channel and atransport channel; the multiplexing/demultiplexing of an MAC servicedata unit (SDU) belonging to one logical channel or different logicalchannels to/from a transport block (TB) transferred to/from the PHYlayer through a transport channel; a scheduling information report;error correction through a hybrid automatic repeat request (HARQ);priority handling between UEs using dynamic scheduling; priorityhandling between the logical channels of one UE using logical channelpriority; and padding.

Different types of data transfer service provided by the MAC sublayer.Each logical channel type defines that information of which type istransferred.

Logical channels are classified into two groups: a control channel and atraffic channel.

i) The control channel is used to transfer only control planeinformation and is as follows.

-   -   Broadcast control channel (BCCH): a downlink channel system for        broadcasting control information.    -   Paging control channel (PCCH): a downlink channel transferring        paging information and system information change notification.    -   Common control channel (CCCH): a channel for transmitting        control information between a UE and a network. This channel is        used for UEs not having an RRC connection with a network.    -   Dedicated control channel (DCCH): a point-to-point bidirectional        channel for transmitting dedicated control information between a        UE and a network. It is used by a UE having an RRC connection.

ii) The traffic channel is used to use only user plane information:

-   -   Dedicated traffic channel (DTCH): a point-to-point channel for        transferring user information and dedicated to a single UE. The        DTCH may be present in both the uplink and downlink.

In the downlink, a connection between a logical channel and a transportchannel is as follows.

A BCCH may be mapped to a BCH. A BCCH may be mapped to a DL-SCH. A PCCHmay be mapped to a PCH. A CCCH may be mapped to a DL-SCH. A DCCH may bemapped to a DL-SCH. A DTCH may be mapped to a DL-SCH.

In the uplink, a connection between a logical channel and a transportchannel is as follows. A CCCH may be mapped to an UL-SCH. A DCCH may bemapped to an UL-SCH. A DTCH may be mapped to an UL-SCH.

3) The RLC sublayer supports three transport modes: a transparent mode(TM), an unacknowledged mode (UM) and acknowledged mode (AM).

An RLC configuration may be applied to each logical channel. In the caseof an SRB, the TM or AM mode is used. In contrast, in the case of a DRB,the UM or AM mode is used.

The RLC sublayer performs the transfer a higher layer PDU; independentsequence numbering with a PDCP; error correction through an automaticrepeat request (ARW); segmentation and re-segmentation; the reassemblyof an SDU; RLC SDU discard; and RLC re-establishment.

4) The PDCP sublayer for a user plane performs sequence numbering;header compression and compression-decompression (corresponding to onlyrobust header compression (RoHC)); user data transfer; reordering andduplicate detection (if there is transfer to a layer higher than thePDCP); PDCP PDU routing (in the case of a split bearer); theretransmission of a PDCP SDU; ciphering and deciphering; PDCP SDUdiscard; PDCP re-establishment and data recovery for RLC AM; and theduplication of a PDCP PDU.

The PDCP sublayer a control plane additionally performs sequencenumbering; ciphering, deciphering and integrity protection; controlplane data transfer; duplication detection; the duplication of a PDCPPDU.

When duplication for a radio bearer is configured by RRC, an additionalRLC entity and an additional logical channel are added to a radio bearerin order to control a duplicated PDCP PDU(s). In the PDCP, duplicationincludes transmitting the same PDCP PDU(s) twice. The first one istransferred to the original RLC entity, and the second one istransferred to an additional RLC entity. In this case, the duplicationcorresponding to the original PDCP PDU is not transmitted to the sametransport block. Different two logical channels may belong to the sameMAC entity (in the case of a CA) or to different MAC entities (in thecase of DC). In the former case, a logical channel mapping restrictionis used to guarantee that a duplication corresponding to the originalPDCP PDU is not transferred to the same transport block.

5) The SDAP sublayer performs i) mapping between a QoS flow and a dataradio bearer and ii) QoS flow ID marking within a downlink and uplinkpacket.

One protocol entity of an SDAP is configured for each PDU session, butexceptionally in the case of dual connectivity (DC), two SDAP entitiesmay be configured.

6) The RRC sublayer performs the broadcasting of system informationrelated to an access stratum (AS) and a non-access stratum (NAS); paginginitiated by 5GC or an NG-RAN; the establishment, maintenance andrelease (additionally including the modification and release of acarrier aggregation and additionally including the modification andrelease of dual connectivity between an E-UTRAN and an NR or within anNR) of an RRC connection between a UE and an NG-RAN; a security functionincluding key management; the establishment, configuration, maintenanceand release of an SRB(s) and a DRB(s); handover and context transfer;control of UE cell selection, re-release and cell selection/reselection;a mobility function including mobility between RATs; a QoS managementfunction, a UE measurement report and report control; the detection of aradio link failure and recovery from a radio link failure; and thetransfer of an NAS message from an NAS to a UE and the transfer of anNAS message from a UE to an NAS.

Network Slicing

A 5G system has introduced a network slicing technology which providesnetwork resources and network functions to an independent slice based oneach service.

As network slicing is introduced, the isolation, independent management,etc. of a network function and network resources can be provided foreach slice. Accordingly, services that are independent for each serviceor user and that are more flexible can be provided by selecting andcombining network functions of the 5G system depending on a service oruser.

A network slice refers to a network that logically integrates an accessnetwork and a core network.

The network slice may include one or more of the followings:

-   -   Core network control plane and user plane function    -   NG-RAN    -   Non-3GPP interworking function (N3IWF) toward a non-3GPP access        network

A function supported for each network slice and network functionoptimization may be different. A plurality of network slice instancesmay provide the same function to different groups of UEs.

One UE may be connected to one or more network slice instances at thesame time via a 5G-AN. One UE may be served at the same time by amaximum of 8 network slices. An AMF instance that serves a UE may belongto each network slice instance that serves the UE. That is, the AMFinstance may be common to a network slice instance that serves the UE.The CN part of a network slice instance(s) that serves a UE is selectedby a CN.

One PDU session belongs to only a specific one network slice instancefor each PLMN. Different network slice instances do not share one PDUsession.

One PDU session belongs to a specific one network slice instance foreach PLMN. Different slices may have slice-specific PDU sessions usingthe same DNN, but different network slice instances do not share one PDUsession.

Single network slice selection assistance information (S-NSSAI)identifies a network slice. Each S-NSSAI is assistant information usedfor a network to select a specific network slice instance. The NSSAI isa set of S-NSSAI(s). The S-NSSAI includes the followings:

-   -   Slice/service type (SST): the SST indicates the operation of a        network slice expected form a viewpoint of a function and        service.    -   Slice differentiator (SD): the SD is optional information that        supplements an SST(s) for selecting a network slice instance        from a plurality of potential network slice instances all of        which comply with an indicated SST.

1) Upon Initial Access, Network Slice Selection

A Configured NSSAI may be configured in a UE by a home PLMN (HPLMN) foreach PLMN. The Configured NSSAI becomes PLMN-specific, and the HPLMNindicates a PLMN(s) to which each Configured NSSAI has been applied.

Upon initial connection of a UE, an RAN selects an initial network slicethat will transfer a message using an NSSAI. To this end, in aregistration procedure, a UE provides a requested NSSAI to a network. Inthis case, when the UE provides the requested NSSAI to the network, a UEwithin a specific PLMN uses only S-NSSAIs belonging to the ConfiguredNSSAI of the corresponding PLMN.

If a UE does not provide an NSSAI to an RAN and an RAN does not select aproper network slice based on the provided NSSAI, the RAN may select adefault network slice.

Subscription data includes the S-NSSAI(s) of a network slice(s) to whicha UE has subscribed. One or more S-NSSAI(s) may be marked as a defaultS-NSSAI. When an S-NSSAI is marked by default, although a UE does nottransmit any S-NSSAI to a network within a Registration Request, thenetwork may serve the UE through a related network slice.

When a UE is successfully registered, a CN notifies an (R)AN of all ofAllowed NSSAIs (including one or more S-NSSAIs) by providing the NSSAIs.Furthermore, when the registration procedure of the UE is successfullycompleted, the UE may obtain an Allowed NSSAI for a PLMN from an AMF.

The Allowed NSSAI has precedence over the Configured NSSAI for the PLMN.Thereafter, the UE uses only an S-NSSAI(s) within the Allowed NSSAIcorresponding to a network slice for a network slice selection-relatedprocedure within the serving PLMN.

In each PLMN, a UE stores a Configured NSSAI and an Allowed NSSAI (ifpresent). When the UE receives an Allowed NSSAI for a PLMN, it overridesthe previously stored Allowed NSSAI for the PLMN.

2) Slice Change

A network may change an already selected network slice instancedepending on a local policy and the mobility, subscription informationchange, etc. of a UE. That is, a set of network slices of a UE may bechanged at any time while the UE is registered with a network.Furthermore, a change of a set of network slices of a UE may beinitiated by a network or under specific conditions.

A network may change a set of allowed network slice(s) with which a UEhas been registered based on a local policy, a subscription informationchange and/or the mobility of the UE. A network may perform such achange during a registration procedure or may notify a UE of a change ofa supported network slice(s) using a procedure capable of triggering aregistration procedure.

Upon changing the network slice, the network may provide the UE with anew Allowed NSSAI and a tracking area list. The UE includes the newNSSAI in signaling according to a mobility management procedure andtransmits the signaling, thereby causing the reselection of a sliceinstance. An AMF supporting the slice instance may also be changed inresponse to a change of the slice instance.

When a UE enters an area in which a network slice is no longeravailable, a core network releases a PDU session for an S-NSSAIcorresponding to a network slice that is no longer available through aPDU session release procedure.

When the PDU session corresponding to the slice that is no longeravailable is released, the UE determines whether the existing trafficcan be routed through a PDU session belonging to another slice using aUE policy.

For a change of a set of used S-NSSAI(s), a UE initiates a registrationprocedure.

3) SMF Selection

A PCF provides a UE with a network slice selection policy (NSSP). TheNSSP associates the UE with an S-NSSAI and is used by the UE in order todetermine a PDU session to which traffic will be routed.

A network slice selection policy is provided for each application of aUE. This includes a rule by which an S-NSSAI can be mapped for each UEapplication. The AMF selects an SMF for PDU session management usingsubscriber information and a local operator policy along with anSM-NSSAI transferred by a UE and DNN information.

When a PDU session for a specific slice instance is established, a CNprovides an (R)AN with an S-NSSAI corresponding to the slice instance towhich the PDU session belongs so that an RAN can access a specificfunction of a slice instance.

Session Management

5GC supports a PDU connectivity service, that is, a service thatprovides the exchange of PDU(s) between a UE and a DN identified by adata network name (DNN) (or an access point name (APN)). The PDUconnectivity service is also supported through a PDU session establishedupon request from the UE.

Each PDU session supports a single PDU session type. That is, when thePDU session is established, it supports the exchange of PDUs of a singletype requested by a UE. The following PDU session types are defined. IPversion 4 (IPv4), IP version 6 (IPv6), Ethernet, and unstructured. Inthis case, the type of PDUs exchanged between a UE and a DN arecompletely transparent in a 5G system.

A PDU session is established using NAS SM signaling exchanged between aUE and an SMF through N1 (upon UE request), modified (upon UE and 5GCrequest), and released (upon UE and 5GC request). Upon request from anapplication server, 5GC may trigger a specific application within a UE.When the UE receives a trigger message, it transfers the correspondingmessage to an identified application. The identified application mayestablish a PDU session with a specific DNN.

An SMF checks whether a UE request complies with user subscriptioninformation. To this end, the SMF obtains SMF level subscription datafrom UDM. Such data may indicate an accepted PDU session type for eachDNN:

A UE registered through a plurality of accesses selects access forsetting up a PDU session.

A UE may request to move a PDU session between 3GPP and non-3GPP access.A determination for moving the PDU session between 3GPP and non-3GPPaccess is made for each PDU session. That is, the UE may have a PDUsession using 3GPP access while another PDU session uses non-3GPPaccess.

Within a PDU session setup request transmitted by a network, a UEprovides a PDU session identity (ID). Furthermore, the UE may provide aPDU session type, slicing information, a DNN, service and a sessioncontinuity (SSC) mode.

A UE may establish a plurality of PDU sessions with the same DN ordifferent DNs at the same time via 3GPP access and/or via non-3GPPaccess.

A UE may establish a plurality of PDU sessions with the same DN servedby a different UPF end N6.

A UE having a plurality of established PDU sessions may be served bydifferent SMFs.

The user plane path of a different PDU sessions belonging to the same UE(the same or different DNNs) may be fully separated between an UPF andAN interfacing with a DN.

5G system architecture can satisfy various continuity requirements ofdifferent application/services within a UE by supporting a session andservice continuity (SCC). A 5G system supports different SSC modes. AnSSC mode associated with a PDU session anchor is not changed while a PDUsession is established.

-   -   In the case of a PDU session to which SSC Mode 1 is applied, a        network maintains continuity service provided to a UE. In the        case of a PDU session of an IP type, an IP address is        maintained.    -   If SSC Mode 2 is used, a network may release continuity service        delivered to a UE. Furthermore, the network may release a        corresponding PDU session. In the case of a PDU session of an IP        type, a network may release an IP address(s) allocated to a UE.    -   If SSC Mode 3 is used, a change of a user plane can be aware by        a UE, but a network guarantees that the UE does not lose        connectivity. In order to permit better service continuity, a        connection through a new PDU session anchor point is established        before a previous connection is terminated. In the case of a PDU        session of an IP type, an IP address is not maintained while an        anchor is deployed again.

An SSC mode selection policy is used to determine the type of SSC modeassociated with an application (or application group) of a UE. Anoperator may previously configure an SSC mode selection policy in a UE.The policy includes one or more SSC mode selection policy rules whichmay be used for a UE to determine the type of SSC mode associated withan application (or a group of applications). Furthermore, the policy mayinclude a default SSC mode selection policy rule which may be applied toall of applications of a UE.

If a UE provides an SSC mode when it requests a new PDU session, an SMFselects whether it will accept the requested SSC mode or whether it willmodify the requested SSC mode based on subscription information and/or alocal configuration. If a UE does not provide an SSC mode when itrequests a new PDU session, an SMF selects a default SSC mode for datanetworks listed within subscription information or applies a localconfiguration for selecting an SSC mode.

An SMF notifies a UE of an SSC mode selected for a PDU session.

Mobility Management

Registration management (RM) is used to register or deregister a UE/userwith/from a network and to establish user context within a network.

1) Registration Management

A UE/user needs to register a network in order to receive service thatrequests registration. Once the UE/user is registered, the UE may updateits own registration with the network in order to periodically maintainreachability (periodical registration update) if applicable, upon moving(mobility registration update), or in order to update its own capabilityor negotiate a protocol parameter again.

An initial registration procedure includes the execution of a networkaccess control function (i.e., user authentication and accessauthentication based on a subscription profile within UDM). As theresults of the registration procedure, the ID of a serving AMF withinthe UDM is registered.

FIG. 10 illustrates RM state models to which the present invention maybe applied. Specifically, FIG. 10(a) shows an RM state model within aUE, and FIG. 10(b) shows an RM state model within an AMF.

Referring to FIG. 10, in order to reflect the registration state of a UEwithin a selected PLMN, two RM states of RM-DEREGISTERED andRM-REGISTERED are used within the UE and the AMF.

In the RM-DEREGISTERED state, the UE is not registered with a network.The valid location or routing information of UE context within the AMFis not maintained. Accordingly, the UE is not reachable by the AMF.However, for example, in order to prevent an authentication procedurefrom being executed for each registration procedure, some UE context maybe still stored in the UE and the AMF.

In the RM-DEREGISTERED state, if the UE needs to receive service thatrequests registration, the UE attempts registration with a selected PLMNusing the initial registration procedure. Alternatively, upon initialregistration, when the UE receives a Registration Reject, the UE remainsin the RM-DEREGISTERED state. In contrast, when the UE receives theRegistration Accept, it enters the RM-REGISTERED state.

-   -   In the RM-DEREGISTERED state, if applicable, the AMF accepts the        initial registration of the UE by transmitting a Registration        Accept to the UE, and enters the RM-REGISTERED state.        Alternatively, if applicable, the AMF rejects the initial        registration of the UE by transmitting a Registration Reject to        the UE.

In the RM-REGISTERED state, the UE is registered with the network. Inthe RM-REGISTERED state, the UE may receive service that requestsregistration with the network.

-   -   In the RM-REGISTERED state, if the tracking area identity (TAI)        of a current serving cell is not present within a list of TAIs        that has been received by the UE from a network, the        registration of the UE is maintained. The UE performs a mobility        registration update procedure so that the AMF can page the UE.        Alternatively, in order to notify a network that the UE is still        in the active state, the UE performs a periodic registration        update procedure when a periodical update timer expires.        Alternatively, in order to update its own capability information        or negotiate a protocol parameter with a network again, the UE        performs a registration update procedure. Alternatively, if the        UE does no longer require registration with a PLMN, the UE        performs a deregistration procedure and enters the        RM-DEREGISTERED state. The UE may determine deregistration from        the network at any time. Alternatively, when the UE receives a        Registration Reject message, a Deregistration message or        performs a local deregistration procedure without the initiation        of any signaling, it enters the RM-DEREGISTERED state.    -   In the RM-REGISTERED state, when the UE does no longer need to        be registered with the PLMN, the AMF performs a deregistration        procedure and enters the RM-DEREGISTERED state. The AMF may        determine the deregistration of the UE at any time.        Alternatively, after an implicit deregistration timer expires,        the AMF performs implicit deregistration at any time. The AMF        enters the RM-DEREGISTERED state after the implicit        deregistration. Alternatively, the AMF performs local        deregistration for the UE that has negotiated deregistration at        the end of communication. The AMF enters the RM-DEREGISTERED        state after local deregistration. Alternatively, if applicable,        the AMF accepts or rejects registration update from the UE. The        AMF may reject UE registration when it rejects the registration        update from the UE.

Registration area management includes a function for allocating orre-allocating a registration area to the UE. The registration area ismanaged for each access type (i.e., 3GPP access or non-3GPP access).

When the UE is registered with a network through 3GPP access, the AMFallocates a set of tracking area (TA)(s) within a TAI list to the UE.When the AMF allocates a registration area (i.e., a set of TAs withinthe TAI list), the AMF may consider various types of information (e.g.,a mobility pattern and an accepted/non-accepted area). The AMP havingthe whole PLMN or all of PLMNs as a serving area may allocate the wholePLMN, that is, a registration area, to the UE in the MICO mode.

A 5G system supports the allocation of a TAI list including different5G-RAT(s) within a single TAI list.

When the UE is registered with a network through non-3GPP access, aregistration area for the non-3GPP access corresponds to a uniquereserved TAI value (i.e., dedicated to the non-3GPP access).Accordingly, there is a unique TA for the non-3GPP access to 5GC, whichis called an N3GPP TAI.

When the TAI list is generated, the AMF includes only a TAI(s)applicable to access through which the TAI list has been transmitted.

2) Connection Management

Connection management (CM) is used to establish and release a signalingconnection between the UE and the AMF. CM includes a function ofestablishing and releasing a signaling connection between the UE and theAMF through N1. The signaling connection is used to enable an NASsignaling exchange between the UE and a core network. The signalingconnection includes both an AN signaling connection for the UE betweenthe UE and the AN and an N2 connection for the UE between the AN and theAMF.

FIG. 11 illustrates CM state models to which the present invention maybe applied. Specifically, FIG. 11 (a) illustrates a CM state shiftwithin a UE, and FIG. 11 (b) shows a CM state shift within an AMF.

Referring to FIG. 11, in order to reflect the NAS signaling connectionof the UE with the AMF, two CM states of CM-IDLE and CM-CONNECTED areused.

The UE in the CM-IDLE state is the RM-REGISTERED state and does not havean NAS signaling connection established with the AMF through N1. The UEperforms cell selection, cell reselection and PLMN selection.

An AN signaling connection, an N2 connection and an N3 connection forthe UE in the CM-IDLE state are not present.

-   -   In the CM-IDLE state, if the UE is not in the MICO mode, it        responds to paging by performing a Service Request procedure (if        it has received it). Alternatively, when the UE has uplink        signaling or user data to be transmitted, it performs a Service        Request procedure. Alternatively, whenever an AN signaling        connection is established between the UE and the AN, the UE        enters the CM-CONNECTED state. Alternatively, the transmission        of an initial NAS message (Registration Request, Service Request        or Deregistration Request) starts to shift from the CM-IDLE        state to the CM-CONNECTED state.    -   In the CM-IDLE state, if the UE is not in the MICO mode, when        the AMF has signaling or the mobile-terminated data to be        transmitted to the UE, it performs a network-triggered service        request procedure by transmitting a paging request to the        corresponding UE. Whenever an N2 connection for a corresponding        UE between the AN and the AMF is established, the AMF enters the        CM-CONNECTED state.

The UE in the CM-CONNECTED state has an NAS signaling connection withthe AMF through N1.

In the CM-CONNECTED state, whenever the AN signaling connection isreleased, the UE enters the CM-IDLE state.

-   -   In the CM-CONNECTED state, whenever an N2 signaling connection        and N3 connection for the UE are released, the AMF enters the        CM-IDLE state.    -   When an NAS signaling procedure is completed, the AMF may        determine to release the NAS signaling connection of the UE.        When the AN signaling connection release is completed, the CM        state within the UE changes to the CM-IDLE. When an N2 context        release procedure is completed, the CM state for the UE within        the AMF changes to the CM-IDLE.

The AMF may maintain the UE in the CM-CONNECTED state until the UE isderegistered from a core network.

The UE in the CM-CONNECTED state may be an RRC Inactive state. When theUE is in the RRC Inactive state, UE reachability is managed by an RANusing assistant information from a core network. Furthermore, when theUE is in the RRC Inactive state, UE paging is managed by the RAN.Furthermore, when the UE is in the RRC Inactive state, the UE monitorspaging using the CN and RAN ID of the UE.

The RRC Inactive state is applied to an NG-RAN (i.e., applied to an NRand E-UTRA connected to 5G CN).

The AMF provides assistant information to the NG-RAN in order to assistthe determination of the NG-RAN regarding whether the UE will be changedto the RRC Inactive state based on a network configuration.

The RRC Inactive assistant information includes a UE-specificdiscontinuous reception (DRX) value for RAN paging during the RRCInactive state and a registration area provided to the UE.

CN assistant information is provided to a serving NG RAN node during N2activation (i.e., registration, a service request or path switch).

The state of an N2 and the N3 reference point is not changed by the UEthat enters the CM-CONNECTED state accompanied by RRC Inactive. The UEin the RRC Inactive state is aware of an RAN notification area.

When the UE is the CM-CONNECTED state accompanied by RRC Inactive, theUE may resume an RRC connection due to uplink data pending, amobile-initiated signaling procedure (i.e., periodical registrationupdate), a response to RAN paging, or when the UE notifies a networkthat it has deviated from the RAN notification area.

When the connection of the UE in a different NG-RAN node within the samePLMN resumes, UE AS context is recovered from an old NG RAN node, andthe procedure is triggered toward a CN.

When the UE is in the CM-CONNECTED state accompanied by RRC Inactive,the UE performs cell selection on a GERAN/UTRAN/EPS and complies with anidle mode procedure.

Furthermore, the UE in the CM-CONNECTED state accompanied by RRCInactive enters the CM-IDLE mode and complies with an NAS procedurerelated to the following cases.

-   -   If an RRC resumption procedure fails,    -   If a movement to the CM-IDLE mode of the UE is required within a        failure scenario that cannot be solved in the RRC Inactive mode.

The NAS signaling connection management includes a function forestablishing and releasing an NAS signaling connection.

The NAS signaling connection establishment function is provided by theUE and the AMF in order to establish the NAS signaling connection of theUE in the CM-IDLE state.

When the UE in the CM-IDLE state needs to transmit an NAS message, theUE initiates a service request or registration procedure in order toestablish a signaling connection to the AMF.

The AMF may maintain the NAS signaling connection until the UE isderegistered from a network based on the preference of the UE, UEsubscription information, a UE mobility pattern and a networkconfiguration.

The procedure of releasing the NAS signaling connection is initiated bya 5G (R)AN node or the AMF.

When the UE detects the release of an AN signaling connection, the UEdetermines that the NAS signaling connection has been released. When theAMF detects that N2 context has been released, the AMF determines thatthe NAS signaling connection has been released.

3) UE Mobility Restriction

A mobility restriction restricts the service access or mobility controlof a UE within a 5G system. A mobility restriction function is providedby a UE, an RAN and a core network.

The mobility restriction is applied to only 3GPP access, but is notapplied to non-3GPP access.

In the CM-IDLE state and the CM-CONNECTED state accompanied by RRCInactive, a mobility restriction is performed by a UE based oninformation received from a core network. In the CM-CONNECTED state, amobility restriction is performed by an RAN and a core network.

In the CM-CONNECTED state, a core network provides a handoverrestriction list for a mobility restriction to an RAN.

The mobility restriction includes an RAT restriction, a forbidden areaand a service area restriction as follows:

-   -   RAT restriction: the RAT restriction is defined as a 3GPP RAT(s)        whose access of a UE is not permitted. A UE within a restricted        RAT is not allowed to initiate any communication with a network        based on subscription information.    -   Forbidden area: a UE is not allowed to initiate any        communication with a network based on subscription information        within a forbidden area under a specific RAT.    -   Service area restriction: it defines an area in which a UE can        initiate cannot initiate communication with a network as        follows:    -   Allowed area: if a UE is allowed by subscription information        within an allowed area under a specific RAT, the UE is allowed        to initiate communication with a network.    -   Non-allowed area: a service area for a UE is restricted based on        subscription information within a non-allowed area under a        specific RAT. The UE and the network are not allowed to initiate        session management signaling for obtaining a service request or        user service (both the CM-IDLE state and the CM-CONNECTED        state). The RM procedure of the UE is the same as that in the        allowed area. A UE within a non-allowed area responds to the        paging of a core network as a service request.

In a specific UE, a core network determines a service area restrictionbased on UE subscription information. Optionally, an allowed area may befine-tuned by a PCF (e.g., based on a UE location, a permanent equipmentidentifier (PEI) or a network policy). The service area restriction maybe changed due to subscription information, a location, a PEI and/or apolicy change, for example. The service area restriction may be updatedduring a registration procedure.

If a UE has an RAT restriction, a forbidden area, an allowed area, anon-allowed area or an area overlapping between them, the UE performs anoperation according to the following priority:

-   -   The evaluation of the RAT restriction has precedence over the        evaluation of any other mobility restriction;    -   The evaluation of the forbidden area has precedence over the        evaluation of the allowed area and the non-allowed area; and    -   The evaluation of the non-allowed area has precedence over the        evaluation of the allowed area.

4) Mobile Initiated Connection Only (MICO) Mode

A UE may indicate the preference of the MICO mode during initialregistration or registration update. The AMF determines whether the MICOmode is permitted for the UE based on a local configuration, thepreference indicated by the UE, UE subscription information and anetwork policy or a combination of them, and notifies the UE of theresults during a registration procedure.

A UE and a core network re-initiates or exits from the MICO mode in thefollowing registration signaling. If the MICO mode is not clearlyindicated within a registration procedure and a registration procedureis successfully completed, the UE and the AMF do not use the MICO mode.That is, the UE operates as a general UE, and the network also treats acorresponding UE as a general UE.

The AMF allocates a registration area to a UE during a registrationprocedure. When the AMF indicates the MICO mode for the UE, theregistration area is not restricted as a paging area size. If the AMFserving area is the whole PLMN, the AMF may provide the UE with the“whole PLMN” registration area. In this case, re-registration with thesame PLMN attributable to mobility is not applied. If a mobilityrestriction is applied to a UE in the MICO mode, the AMF allocates anallowed area/non-allowed area to the UE.

When the AMF indicates the MICO mode for the UE, the AMF considers thatthe UE is always unreachable during the CM-IDLE state. The AMF rejectsany request for downlink data transfer for a corresponding UE that is inthe MICO mode and the CM-IDLE state. The AMF also delays downlinktransport, such as SMS or location service through the NAS. A UE in theMICO mode may be reachable for mobile-terminated data or signaling onlywhen the UE is in the CM-CONNECTED mode.

The AMF may provide an RAN node with pending data indication when a UEin the MICO mode can immediately transport mobile-terminated data and/orsignaling when the UE switches to the CM-CONNECTED mode. When the RANnode receives the indication, the RAN node considers the informationwhen it determines user inactivity.

A UE in the MICO mode does not need to listen to paging during theCM-IDLE state. The UE in the MICO mode may stop any AS procedure withinthe CM-IDLE state until it starts switching from the CM-IDLE to theCM-CONNECTED mode due to one of the following reasons.

-   -   If a change (e.g., configuration change) within the UE requires        registration update to a network    -   If a periodic registration timer expires    -   If MO data is pending    -   If MO signaling is pending

Quality of Service (QoS) Model

QoS is a technology for the smooth transfer service of various traffic(mail, data transmission, audio and video) to a user depending on eachcharacter.

A 5G QoS model supports a framework-based QoS flow. The 5G QoS modelsupports both a QoS flow that requires a guaranteed flow bit rate (GFBR)and a QoS flow that does not require the GFBR.

The QoS flow is the finest granularity for QoS classification in a PDUsession.

A QoS flow ID (QFI) is used to identify a QoS flow within a 5G system.The QFI is unique within a PDU session. User plane traffic having thesame QFI within a PDU session receives the same traffic transferprocessing (e.g., scheduling and an admission threshold). The QFI istransferred within an encapsulation header on N3 (and N9). The QFI maybe applied to a different payload type of a PDU (i.e., an IP packet,unstructured packet and Ethernet frame).

In this specification, for convenience of description, “QoS” and a “QoSflow” are interchangeably used. Accordingly, in this specification,“QoS” may be construed as meaning a “QoS flow”, and “QoS” may beconstrued as meaning a “QoS flow.”

Within a 5G system, QoS flows may be controlled by an SMF upon PDUsession setup or QoS flow establishment/modification.

If applicable, all of QoS flows have the following characteristics:

-   -   QoS profile previously configured in the AN or provided from the        SMF to the AN via the AMF through the N2 reference point;    -   One or more networks provided from the SMF to the UE via the AMF        through the N1 reference point—provided QoS rule(s) and/or one        or more UE-derived QoS rule(s)    -   SDF classification provided from the SMF to the UPF through the        N4 reference point and QoS-related information (e.g.,        session-aggregate maximum bit rate (AMBR)).

The QoS flow may become a “guaranteed bit rate (GBR)” or a“non-guaranteed bit rate (non-GBR)” depending on the QoS profile. TheQoS profile of the QoS flow includes the following QoS parameters:

i) With respect to each of QoS flows, QoS parameters may include thefollowings:

-   -   5G QoS indicator (5QI): the 5QI is a scalar for referring to 5G        QoS characteristics (i.e., control QoS transfer handling access        node-specific parameters for a QoS flow, for example, scheduling        weight, an admission threshold, a queue management threshold and        a link layer protocol configuration).    -   Allocation and retention priority (APR): the ARP includes a        priority level, a pre-emption capability and pre-emption        vulnerability. The priority level defines the relative        importance of a resource request. This is used to determine        whether a new QoS flow will be accepted or rejected if resources        are restricted and to used to determine whether the existing QoS        flow will pre-empt resources while the resources are restricted.

ii) Furthermore, only in the case of each GBR QoS flow, QoS parametersmay further include the followings:

-   -   GFBR—the uplink and downlink;    -   Maximum flow bit rate (MFBR)—the uplink and downlink; and    -   Notification control.

iii) Only in the case of a non-GBR QoS flow, QoS parameters may furtherinclude the following: Reflective QoS attribute (RQA)

There are supported methods of controlling the following QoS flows:

1) In the case of the non-GBR QoS flow: if a standardized 5QI or apreviously configured 5QI is used, a 5QI value is used as the QFI of theQoS flow and a default ARP is previously configured in the AN;

2) In the case of the GBR QoS flow: if a standardized 5QI or apreviously configured 5QI is used, a 5QI value is used as the QFI of theQoS flow. A default ARP is transmitted to the RAN when a PDU session isestablished. Whenever the NG-RAN is used, the user plane (UP) of the PDUsession is activated;

3) In the case of the GBR and non-GBR QoS flow: an allocated QFI isused. A 5QI value may be standardized, previously configured or notstandardized. The QoS profile and QFI of the QoS flow may be provided tothe (R)AN through N2 when a PDU session is established or when a QoSflow is established/changed. Whenever the NG-RAN is used, the user plane(UP) of the PDU session is activated.

A UE may perform the marking and classification (i.e., the associationof UL traffic for a QoS flow) of UL user plane traffic based on a QoSrule. Such rules may be explicitly provided to the UE (when a PDUsession is established or a QoS flow is established) or may have beenpreviously configured in the UE or may be implicitly derived by the UEby applying reflective QoS.

The QoS rule may include a unique QoS rule ID within a PDU session, theQFI of an associated QoS flow, and one or more packet filters andprecedence value. Additionally, with respect to an allocated QFI, theQoS rule may include QoS parameters related to a UE. One or more QoSrules associated with the same QoS flow (i.e., having the same QFI) maybe present.

The default QoS rule may be necessary for all of PDU sessions. Thedefault QoS rule may be a unique QoS rule of a PDU session that may notinclude a packet filter (In this case, the highest precedence value(i.e., the lowest priority) must be used). If the default QoS rule doesnot include a packet filter, the default QoS rule defines the processingof packets not matched with another QoS rule in a PDU session.

The SMF performs binding between SDFs for a QoS flow depending on theQoS of an SDF and service requirements. The SMF allocates a QFI to a newQoS flow, and derives the QoS parameter of the new QoS flow frominformation provided by the PCF. If applicable, the SMF may provide an(R)AN with a QFI along with a QoS profile. The SMF provides an SDFtemplate (i.e., a set of packet filters associated with the SDF receivedfrom the PCF) along with SDF priority, QoS-related information andcorresponding packet marking information (i.e., a QFI, a differentiatedservices code point (DSCP) value and optionally enables theclassification, bandwidth application and marking of user plane trafficusing reflective QoS indication for a UPF). If applicable, the SMFgenerates QoS rule(s) for a PDU session by allocating unique QoS ruleIDs within a PDU session to which the QFI of a QoS flow has been added,configuring packet filter(s) for the UL part of the SDF template, andsetting QoS rule priority in the SDF priority. The QoS rule is providedto a UE that enables the classification and marking of UL user planetraffic.

FIG. 12 illustrates classification and user plane marking for a QoS flowand the mapping of a QoS flow to AN resources according to an embodimentof the present invention.

1) Downlink

An SMF allocates a QFI for each QoS flow. Furthermore, the SMF derivesQoS parameters from information provided by a PCF.

The SMF provides an (R)AN with the QFI along with a QoS profileincluding the QoS parameters of a QoS flow. Furthermore, when a PDUsession or QoS flow is established, the QoS parameters of the QoS flowis provided to the (R)AN as the QoS profile through N2. Furthermore,whenever an NG-RAN is used, a user plane is activated. Furthermore, QoSparameters may be previously configured in the (R)AN for a non-GBR QoSflow.

Furthermore, the SMF provides an UPF with an SDF template (i.e., a setof packet filters associated with the SDF received from the PCF) alongwith SDF preference and a corresponding QFI so that the UPF can performthe classification and marking of a downlink user plane packet.

Downlink inflow data packets are classified based on the SDF templateaccording to the SDF preference (without the initiation of additional N4signaling). A CN classifies user plane traffic belonging to a QoS flowthrough N3 (and N9) user plane marking using the QFI. The AN binds theQoS flow with AN resources (i.e., a DRB in the case of the 3GPP RAN). Inthis case, a relation between the QoS flow and the AN resources is notrestricted to 1:1. The AN may configure the AN resources necessary tomap a QoS flow to a DRB so that a UE may receive the QFI (and reflectiveQoS may be applied).

If matching is not discovered, when all of QoS flows are related to oneor more DL packet filters, the UPF may discard a DL data packet.

Characteristics applied to process downlink traffic are as follows:

-   -   The UPF maps user plane traffic to the QoS flow based on the SDF        template.    -   The UPF performs session-AMBR execution and performs PDU        counting for charging support.    -   The UPF may transmit the PDUs of a PDU session in a single        tunnel between 5GC and the (A)AN, and the UPF may include the        QFI in an encapsulation header.    -   The UPF performs transmission level packet marking in the        downlink (e.g., sets DiffSery code in an outer IP header).        Transmission level packet marking is based on 5QI and the ARP of        an associated QoS flow.    -   The (R)AN maps PDUs from a QoS flow to access-specific resources        based on a QFI, related 5G QoS characteristics and parameters by        considering an N3 tunnel associated with a downlink packet.    -   If reflective QoS is applied, a UE may generate a new derived        QoS rule (or may be called a “UE-derived QoS rule”). A packet        filter within the derived QoS rule may be derived from a DL        packet (i.e., the header of the DL packet). The QFI of the        derived QoS rule may be configured depending on the QFI of the        DL packet.

2) Uplink

The SMF generates QoS rule(s) for a PDU session by allocating a QoS ruleID, adding the QFI of a QoS flow, setting packet filter(s) in the uplinkpart of an SDF template, and setting QoS rule precedence in SDFprecedence. The SMF may provide a UE with the QoS rules in order for theUE to perform classification and marking.

The QoS rule includes a QoS rule ID, the QFI of a QoS flow, one or morepacket filters and preference values. The same QFI (i.e., the same QoSflow) and one or more QoS rules may be associated.

A default QoS rule is required for each PDU session. The default QoSrule is the QoS rule of a PDU session not including a packet filter (Inthis case, the highest precedence value (i.e., the lowest priority) isused). If the default QoS rule does not include a packet filter, thedefault QoS rule defines the processing of a packet not matched with anyanother QoS rule within the PDU session.

The UE performs the classification and marking of uplink user planetraffic. That is, the UE associates uplink traffic with the QoS flowbased on the QoS rule. The rule may be explicitly signaled through N1(when a PDU session is established or when a QoS flow is established ormay be previously configured in the UE or may be implicitly derived bythe UE from reflected QoS.

In the UL, the UE evaluates an UL packet with respect to the packetfilter of the QoS rule based on the precedence value of the QoS rule(i.e., in order of increasing precedence value) until a matching QoSrule (i.e., the packet filter is matched with the UL packet) isdiscovered. The UE binds the UL packet to the QoS flow using a QFI inthe corresponding matching QoS rule. The UE binds the QoS flow and theAN resources.

If matching is not discovered and a default QoS rule includes one ormore UL packet filters, the UE may discard an UL data packet.

Characteristics applied to process uplink traffic are as follows:

-   -   A UE may use stored QoS rules in order to determine mapping        between UL user plane traffic and a QoS flow. The UE may mark an        UL PDU with the QFI of a QoS rule including a matching packet        filter, and may transmit the UL PDU using corresponding        access-specific resources for a QoS flow based on mapping        provided by an RAN.    -   The (R)AN transmits the PDU through an N3 tunnel with respect to        an UPF. When an UL packet passes through a CN from the (R)AN,        the (R)AN includes a QFI in the encapsulation header of the UL        PDU and selects the N3 tunnel.    -   The (R)AN may perform transmission level packet marking in the        uplink. The transmission level packet marking may be based on        the ARP of a QoS flow associated with a 5QI.    -   A UPF checks whether the QFIs of UL PDUs are provided to the UE        or are aligned (e.g., in the case of reflective QoS) with QoS        rules implicitly derived by the UE.    -   The UPF performs session-AMBF execution and counts a packet for        charging.

In the case of an UL classifier PDU session, UL and DL session-AMBRsneed to be performed on an UPF that supports an UL classifier function.Furthermore, the DL session-AMBR needs to be separately performed in allof UPFs that terminate an N6 interface (i.e., an interaction betweenUPFs is not required).

In the case of a multi-home PDU session, UL and DL session-AMBRs areapplied to an UPF that supports a branch point function. Furthermore,the DL session-AMBR needs to be separately performed in all of UPFs thatterminate the N6 interface (i.e., an interaction between UPFs is notrequired).

The (R)AN needs to perform a maximum bit rate (UE-AMBR) restriction inthe UL and DL for each non-GBR QoS flow. When the UE receives asession-AMBR, it needs to perform a PDU session-based UL raterestriction for non-GBR traffic using the session-AMBR. The raterestriction execution for each PDU session is applied to a flow thatdoes not require a guaranteed flow bit rate. The MBR per SDF ismandatory to a GBR QoS flow, but is optional for a non-GBR QoS flow. TheMBR is performed in the UPF.

QoS control for an unstructured PDU is performed in a PDU session level.When the PDU session is established for the transmission of theunstructured PDU, the SMF provides the UPF and the UE with a QFI to beapplied to any packet of the PDU session.

Reflective QoS

Reflective QoS means a method for a UE to determine a QoS flow of theuplink corresponding to the downlink by reflecting a QoS flow of thedownlink.

The support of reflective QoS through an AN is under 5GC control.Reflective QoS may be achieved by generating a QoS rule derived based ondownlink traffic received by a UE. Reflective QoS and non-reflective QoSmay be applied at the same time within the same PDU session. In the caseof traffic influenced by reflective QoS, an UL packet may obtain thesame QoS marking as that of a reflected DL packet.

In the case of a UE supporting a reflective QoS function, if thereflective QoS function is controlled by 5GC with respect to sometraffic flows, the corresponding UE may generate a (derived) QoS rulefor uplink traffic based on received downlink traffic. Furthermore, theUE may use the (derived) QoS rule to determine mapping between theuplink traffic and a QoS flow. Accordingly, in accordance withreflective QoS, although a UE does not separately receive a QoS rule fordetermining a QoS flow of the uplink from a network, the UE mayautonomously generate a QoS rule based on the QoS flow of the downlinkand determine a QoS flow of the uplink corresponding to the downlink(i.e., determines mapping between uplink traffic and the QoS flow).

The derived QoS rule of the UE may include the following parameters:

-   -   (UL) packet filter    -   QFI    -   Precedence value

The (UL) packet filter may be derived based on a received DL packet andmay be used to filter/distinguish UL packets/traffic to which thederived QoS rule will be applied. The UE may filter/distinguish ULpackets/traffic to which the derived QoS rule will be applied byapplying an (UL) packet filter, and may perform QoS marking on thefiltered/distinguished UL packet using a QFI.

A UE not supporting reflective QoS needs to neglect the indication ofreflective QoS.

When reflective QoS is activated through a user plane, a precedencevalue for all of derived QoS rules may be set as a standardized value.If reflective QoS is activated through a control plane (i.e., a QoSflow, a PDU session), a precedence value for a derived QoS rule withinthe range of control plane activation may be set as a signaled valuethrough the control plane.

If user plane reflective QoS is available by 5GC, the UPF may include areflective QoS indication (RQI) indicative of the activation ofreflective QoS in an encapsulation header (may be referred to as an “NG3(encapsulation) header”) through an N3 reference point along with a QFI.

Reflective QoS may be activated through a user plane and a controlplane. 5GC may determine whether reflective QoS will be activatedthrough the control plane or will be activated through the user planebased on an access type and policy.

If 5GC has determined reflective QoS activation through the user (U)plane, the SMF may include a QoS rule (or transmit it to the UPF)including an indication indicating that the reflective QoS must beactivated by reflecting the user plane. If the UPF is matched with theQoS rule and a DL packet including the indication indicative of theactivation of the reflective QoS is received, the UPF may include an RQIin the encapsulation header of the N3 reference point. Reflective QoSactivation through the user plane may be used to avoid out-of-bandsignaling (e.g., signaling through a non-3GPP access network).

If 5GC has determined reflective QoS activation through the control (C)plane, the SMF may include the RQI in the QoS rule transmitted to the UEthrough the N1 interface. If the UE receives a DL packet matched withthe QoS rule including the RQI, the UE may generate a UE-derived QoSrule.

Furthermore, 5GC may also support the inactive function of reflectiveQoS.

-   -   Reflective QoS support through the RAN under the control of a        network: the network determines QoS to be applied to DL traffic,        and a UE reflects the DL QoS in associated UL traffic. When the        UE receives a DL packet to which reflective QoS must be applied,        the UE generates a new implicit QoS rule. The implicit QoS rule        may be referred to as a “derived QoS rule” in this        specification. The packet filter of the implicit QoS rule is        derived from the header of the DL packet. Reflective QoS        indication may be signaled or may not be signaled through a        control (C)-plane or inband. The implicit rule (derived through        reflective QoS) may have higher or lower priority than the        explicitly signaled QoS rule.

As may be seen from the above contents, a method of indicatingreflective QoS includes i) a method of explicitly transmittingsignaling, ii) an inband method of transmitting data marked with theindication of reflective QoS, and iii) a method for a UE to directlydetect reflective QoS without any signaling/marking.

Prior to a more detailed description of such a reflective QoS indicationmethod, a network structure and a bearer mapping method for uplinktraffic to which the present invention may be applied are firstdescribed.

FIG. 13 is a diagram illustrating 5G system architecture to which thepresent invention may be applied. This drawing is a more simplifieddrawing of FIG. 6. The description described in FIG. 6 may beidentically applied.

Referring to FIG. 13, the 5G system architecture may include variouselements (i.e., network functions (NF)). This drawing illustrates anapplication function (AF), a data network (DN), a user plane function(UPF), a control plane function (CPF), a (radio) access network ((R)AN),and a user equipment (UE) corresponding to some of the various elements.

In a 3GPP system, a conceptual link that connects NFs within a 5G systemis defined as a reference point. The following illustrates referencepoints included in the 5G system architecture represented in thisdrawing.

-   -   NG1: a reference point between the UE and the CPF    -   NG2: a reference point between the (R)AN and the CPF    -   NG3: a reference point between the (R)AN and the UPF    -   NG4: a reference point between the UPF and the CPF    -   NG5: a reference point between the CPF and the AF    -   NG6: a reference point between the UPF and the DN

FIG. 14 illustrates a QoS flow mapping method for uplink traffic of a UEto which the present invention may be applied.

Referring to FIG. 14, a UE routes uplink packets to different QoS flowsbased on a packet filter allocated to a QoS rule. The UE preferentiallyevaluates the uplink packet filter of the QoS rule having the lowestevaluation priority index with respect to matching. If matching is notdiscovered, the UE performs the evaluation of a packet filter present inthe QoS rule in increasing order of evaluation priority index. Thisprocedure needs to be executed until matching is discovered or untilpacket filters present in all of QoS rules are evaluated. If matching isdiscovered, the uplink data packet is transmitted through a QoS flowdetermined by a matched QoS rule. If matching is not discovered, theuplink data packet needs to be transmitted through a QoS flow to whichany uplink packet filter has not been allocated. If one or more uplinkpacket filters are allocated to all of QoS rules, the UE must discardthe uplink data packets.

In 5G, unlike in EPC, a bearer for QoS is not separately produced, butan UP function performs QoS marking (operation of marking/indicating aQFI) on an NG3 header according to a rule transmitted by a CP function.A method of providing QoS based on the QoS marking has been describedabove. In the case of reflective QoS, when the UP function provides a UEwith indication to use reflective QoS, the UE may generate an uplink(packet) filter based on a downlink data packet (or traffic), and mayproduce an (uplink QoS) rule for marking the same QoS marking as that ofa downlink data packet (or traffic) in an uplink data packet (ortraffic) using the generated uplink (packet) filter. In this case, theCP function can support the uplink QoS of the UE without directlyindicating a rule for the uplink in the UE.

In accordance with such reflective QoS, there is an effect in that theCP function can simply support the uplink QoS of a UE through onlyindication to apply reflective QoS without directly providing a QoS rulewith respect to temporarily generated data. In this case, if suchreflective QoS is used, there is a problem in that the UE continues togenerate and store a (derived) QoS rule in order to support thereflective QoS. As the number of (derived) QoS rules that need to bemanaged/stored by the UE is increased, the UE's overhead is increasedand a data processing speed is reduced because the number of (derived)QoS rules that must be checked by the UE until a default QoS rule isapplied is increased.

Accordingly, this specification proposes a method ofdiscarding/deleting, by a network node, a QoS rule generated (derived)by a UE for reflective QoS by providing a reflective QoS use timer valuewhen the timer expires (expire), while the network node providessignaling for reflective QoS to the UE. A method of indicatingreflective QoS basically includes three methods to be described later.Such a timer concept may be applied to Method 1 and Method 2 of thethree methods.

Reflective QoS may be indicated in a UE through C-plane signaling(method 1), inband signaling (method 2), and non-signaling method(method 3).

1. The method 1 is a method for a network node to indicate ReflectiveQoS through C-plane signaling. That is, this method is a method ofdirectly indicating (i.e., explicitly indicating reflective QoS throughcontrol signaling), by a CP function, with respect to a UE so that QoS(or QoS flow) is identically used/configured between a downlink (flow)and a corresponding uplink (flow) through control signaling (e.g., thismethod is used if QoS control for an uplink data packet whosesource-destination addresses are exchanged with a downlink data packetis necessary). The method 1 has a small signaling message size becauseit is not necessary for the CP function to directly transfer filterinformation for the uplink and QoS information (e.g., QFI information)to a UE, but has a disadvantage in that separate (control) signaling isgenerated.

2. The method 2 is a method for a network node to indicate reflectiveQoS through inband signaling. In accordance with the method 2, a networknode may transmit an indicator indicating whether reflective QoS must beapplied along with QoS marking in an NG3 (encapsulation) header or aradio header while transmitting data. Accordingly, the method 2 has anadvantage in that reflective QoS can be indicated/applied even withoutadditional (control) signaling, but has a disadvantage in thatadditional information must be added to the NG3 (encapsulation) headeror a radio header. Accordingly, there may be a problem in thatindication for reflective QoS is also lost when a data loss according tocongestion is generated in a process for a network node to transmit datato a UE.

3. In the method 3, a network node does not transmit any signalingrelated to reflective QoS, and may autonomously determine that a UE doesnot have QoS information (e.g., information about a QoS flow, QFI) aboutan uplink flow mapped to the downlink and may apply the reflective QoS.In the case of the method 3, there is no signaling overhead, but thereis no margin that a default QoS (rule) may be applied to the uplink. Ina conventional technology, when an uplink flow is generated, a defaultQoS (Rule) was applied if a TFT suitable for the uplink flow is notpresent. In accordance with the method 3, however, not a default QoS(rule), but reflective QoS is applied. Accordingly, unconditionalreflective QoS is applied to a (uplink) flow mapped to a downlink, andit is difficult to support QoS by separating the uplink and thedownlink. In order to support this, separate QoS rule update throughexplicit signaling must be performed.

In a process of producing a PDU session, the CP function may determinethat reflective QoS will be indicated using which method. The CPfunction may determine whether reflective QoS will be used, a reflectiveQoS activation indication method and/or a deactivation indication methodif the reflective QoS is used, based on reflective QoS capabilityinformation (e.g., a user plane activation capability, a control planeactivation capability, a user plane deactivation capability, a controlplane deactivation capability), an operator policy, information (e.g.,an APN/DNN and a PDU type) about a PDU session, subscriptioninformation, etc., transmitted by a UE.

For example, in order to reduce control plane signaling, the CP functionmay determine a user plane activation/deactivation method (i.e., areflective QoS activation/deactivation indication method through theuser plane) as the reflective QoS activation/deactivation method. The CPfunction may indicate whether determined reflective QoS will be used, areflective QoS activation method and/or reflective QoS deactivationmethod with respect to a UE. The UE may determine whether reflective QoSwill be used/activated based on the reflective QoS-related informationreceived from the CP function. The reflective QoS-related informationfrom the CP function may be transmitted to the UE through a PDU sessionaccept message. In this case, the UE may determine whether thereflective QoS will be used based on the received PDU session acceptmessage, and an embodiment related to it is described hereinafter inconnection with FIG. 15.

If the method 1 is used, the UE may apply reflective QoS to an (uplink)flow indicated by corresponding signaling if there is explicit signalingfrom the CP function. If the method 2 is used, the UE may monitor theheader of a downlink data packet and apply reflective QoS to aspecific/indicated (IP/QoS/uplink) flow if reflective QoS (indication)is marked in the corresponding header. If the method 3 is used, the UEmay apply reflective QoS to uplink flow/data/traffic mapped to areceived downlink flow/data/traffic regardless of a reflective QoS(indication) mark within the head of a downlink data packet.

If it is determined that reflective QoS is not used, the UE maydetermine QoS (flow) of the uplink based on only a current QoS rulewithout the need to determine whether reflective QoS will beapplied/used by monitoring the header of downlink data.

In the reflective QoS activation method, whether the control plane willbe used or the user plane will be used may be determined based onsubscription information or the capability of a UE. For example, inorder to use the user plane activation method as the reflective QoSactivation method, the AS layer of the UE needs to check whetherreflective QoS indication is present by continuing to monitor a packet.Such an operation may be a burden on a simple UE, such as Internet ofThings (loT), or a UE that must operate with low power. Accordingly,with respect to the corresponding UE, the user plane activation methodmay not be determined as a reflective QoS activation method.

The reflective QoS deactivation method may be differently determinedindependently/regardless of a reflective QoS activation method. Forexample, reflective QoS has been activated through the user plane, butmay be deactivated through the control plane. In order to support thedeactivation method through the user plane, a UE may receive indicationto use the user plane deactivation method from a network and may drive atimer if reflective QoS indication is present in data (or a datapacket). Accordingly, in the case of the user plane deactivation method,a network node must explicitly transmit reflective QoS indication to aUE so that the UE can drive a timer. If reflective QoS is activatedthrough the control plane, the UE may not set the timer. In this case,the UE cannot perform the reflective QoS deactivation method through theuser plane.

FIG. 15 is a flowchart illustrating a method of determining whetherreflective QoS will be used and a reflective QoS indication method in aprocess of setting up a PDU session according to an embodiment of thepresent invention. In this specification, the PDU session setupprocedure for producing a PDU session may be referred to as a PDUsession establishment procedure.

1. A UE may transmit a PDU session setup request message to a CPfunction. In this case, the PDU session setup request message may haveincluded reflective QoS capability information regarding whether the UEcan perform the reflective QoS.

2. The CP function may check context information of the UE insubscription data.

3. The CP function may determine whether reflective QoS will be used anda reflective QoS indication method for the UE if the reflective QoS isused.

4. The CP function and an UP function may set up a user plane. Thereflective QoS indication method determined by the CP function in step 3may be shared with the UP function.

5. The CP function may transmit a PDU session setup complete message tothe UE as a response to the PDU session setup request message. In thiscase, the PDU session setup complete message may have includedinformation about a reflective QoS indication method.

Referring to the flowchart of FIG. 15, after checking the context of theUE in step 26, a network node (e.g., the CP function) determines whetherreflective QoS will be used and a reflective QoS indication method ifthe reflective QoS is used, based on reflective QoS capabilityinformation, session information and/or subscription information of theUE received from the UE in step 1. In step 4, the CP function may notifythe UP function of whether reflective QoS will be used and thereflective QoS use method for the PDU session. In step 5, the CPfunction may notify the UE of whether reflective QoS will be used and/orthe reflective QoS indication method.

The aforementioned methods 1 to 3 are described in more detail belowwith reference to respective drawings.

Ga. Method 1: method of directly indicating reflective QoS with respectto UE through signaling

FIG. 16 is a flowchart illustrating a reflective QoS indication methodaccording to the method 1 of the present invention. In relation to thisflowchart, the description of the method 1 described above may beapplied identically/similarly, and a redundant description thereof isomitted.

1. A UE may set up a PDU session and transmit/receive data to/from anetwork node(s) based on the QoS rule received in the PDU session setupprocess (refer to FIG. 15).

2. If a UP function discovers a new IP flow (may be applied to the caseof a non-IP flow), the UP function may notify a CP function that the newflow has been generated/discovered and request corresponding QoS to theCP function.

3. The CP function may transmit both a DL QoS rule and UL QoS rule forthe corresponding IP flow to the UP function (and/or transmit only theDL QoS rule to the UP function, and the UP function may directlygenerate/derive the UL QoS rule based on the DL QoS rule by checkingreflective QoS indication) while transmitting QoS (to the CP function,the UE and/or the AN) with respect to the corresponding IP flow, and mayalso transmit the indication of reflective QoS use.

In this case, the DL QoS rule may correspond to a rule which is used tofilter a DL data packet (or flow) to which specific QoS will bemarked/applied and to perform the QoS marking. The UL QoS rule maycorrespond to a rule which is used to filter an UL data packet (or flow)to which specific QoS will be marked/applied and to perform the QoSmarking.

Furthermore, the CP function may additionally transmit a timer valueregarding time when reflective QoS is valid to the UP function. The UPfunction may use the DL and/or UL QoS rule only until the correspondingtimer expires. The UP function may immediately start the timer when thetimer is received.

The CP function may indicate IP flow information and timer informationto which the reflective QoS will be applied through control signaling(e.g., NAS signaling or AS signaling) with respect to the UE and/or theAN. The UE and/or the AN that have received the IP flow information andtimer information may immediate start the timer.

4. The UP function may apply QoS (or QoS marking) based on the rule(e.g., the DL QoS rule and/or the UL QoS rule) produced through thereflective QoS while the reflective QoS is applied to a specific QoSflow indicated by the CP function. This operates in the same manner asthat general QoS is applied (or QoS marking) according to a DL QoS ruleif there is a (downlink) flow mapped/related to the reflective QoS(i.e., satisfying the DL QoS rule).

5. If the reflective QoS is applied, when the UE receives a downlinkdata packet/flow in the state in which an RQI has been marked (orreflective QoS is indicated), the UE may generate a derived QoS rule(based on the downlink data packet/flow) for an uplink data packet/flow(or may be abbreviated as an “uplink packet/flow”) mapped to thedownlink data packet/flow. The UE starts the timer related to thecorresponding derived QoS rule.

6. The UE may filter/distinguish the subject on which the QoS markingwill be performed by applying the derived QoS rule generated by thereflective QoS rule to the uplink data packets/flows, and may transmitthe uplink data packets/flows after performing the QoS marking on thefiltered/distinguished uplink data packets/flows. In this case, a QFIused when the QoS marking is performed on the uplink data packets/flowsmay have been included in the derived QoS rule, and may be the same as aQFI QoS-marked in the downlink data packet/flow.

7. Thereafter, if the timer for a specific derived QoS rule expires, theUE and the UP function may delete the derived QoS rule.

8. Thereafter, a flow corresponding to previously used reflective QoSmay reach the UP function.

9. Signaling for reflective QoS, such as that of step 3, may betransmitted/received through the flow detection process of step 2.

10-11. While a corresponding derived QoS rule is valid, the UE and/orthe UP function may operate based on the reflective QoS rule accordingto the present embodiment.

The CP function can prevent a rule (e.g., the DL QoS rule, the UL QoSrule and/or the derived QoS rule) from being deleted/expiring bytransmitting a rule/indication for reflective QoS again before the timerexpires.

If the method 1 is used, there may be an effect in that there is norestriction to the size of a timer value because the network nodedirectly provides signaling regarding a reflective QoS application, butadditional (control) signaling is generated.

Na. Method 2: indication method through inband signaling (packetmarking) with respect to a UE

FIG. 17 is a flowchart illustrating a reflective QoS indication methodaccording to the method 2 of the present invention. In relation to thisflowchart, the description of the aforementioned flowchart of FIG. 16and the method 2 may be applied identically/similarly, and a redundantdescription thereof is omitted.

1. A UE may set up a PDU session and may transmit/receive data to/from anetwork node(s) based on a received QoS rule in the PDU session setupprocess (refer to FIG. 15).

2. If an UP function discovers a new IP flow (applicable to the case ofa non-IP flow), the UP function may notify a CP function that the newflow has been generated/discovered and request corresponding QoS to theCP function.

3. The CP function may transmit QoS information (e.g., the indication ofReflective QoS use, QoS (or a DL/UL QoS rule), information on IP flow towhich reflective QoS will be applied and/or timer information) for acorresponding IP flow to the UP function and the AN.

4. The UP function may transmit downlink data, QoS marking (e.g., aQFI), reflective QoS indication (e.g., an RQI) and/or a timer to the UE.In this case, the UP function may apply QoS (or QoS marking) to uplinkdata based on a rule (e.g., the DL QoS rule and/or the UL QoS rule)produced/received through the reflective QoS during the time when thereflective QoS is applied to a corresponding IP flow. The UP functionmay start the corresponding timer along with the transmission of thetimer.

Referring to steps 3 and 4, the method 2 is different from the method 1in that the CP function does not directly transmit QoS information tothe UE and transmits the QoS information to only the UP function and theAN. Instead, the UP function may transmit marking/indication (i.e., anRQI) indicative of a Reflective QoS application and the timer to the UEin an NG3 header as QoS information in addition to the QoS marking whiletransmitting downlink data. In this specification, for convenience ofdescription, downlink data and QoS-related information may be expressedas being transmitted through a “downlink data packet/flow.” Such a“downlink data packet/flow” may be abbreviated as a “downlink packet.”

5. The UE that has received the QoS information may produce a derivedQoS rule based on the downlink data packet/flow and use/apply thederived QoS rule. In this case, the UE may generate a packet filterincluded in the derived QoS rule based on the downlink data packet/flow,and may check whether the same derived QoS rule as the newly generatedderived QoS rule has been previously stored using the generated packetfilter (e.g., by comparing the packet filter with another derived QoSrule). If the same derived QoS rule has been previously stored, the UEmay reset the timer corresponding to/associated with the correspondingderived QoS rule and apply the reflective QoS using the correspondingderived QoS rule. If the same derived QoS rule has not been previouslystored, the UE may apply the reflective QoS using the newly generatedderived QoS rule and start the received timer.

6. The UE may filter/distinguish the subject on which the QoS markingwill be performed by applying the derived QoS rule to the uplink datapackets/flows, and may transmit the filtered/distinguished uplink datapackets/flows after performing the QoS marking on thefiltered/distinguished uplink data packets/flows. In this case, a QFIused to perform the QoS marking on the uplink data packet/flow may havebeen included in the derived QoS rule, and may be the same as a QFIQoS-marked to a downlink data packet/flow.

7. Thereafter, when the timer expires, the UE and the UP function maydelete all of rules (e.g., the DL QoS rule, the UL QoS rule and/or thederived QoS rule) that have been generated or are being stored.

8. Thereafter, a flow corresponding to previously used reflective QoSmay reach the UP function.

9. Signaling for reflective QoS, such as that of step 3, may betransmitted/received through the flow detection process of previous step2.

10-11. While reflective QoS is valid, the UE and/or the UP function mayoperate based on reflective QoS according to the present embodiment.

In an embodiment of the method 2, the UP function may be restricted asincluding the timer and reflective QoS indication in the NG3 header andtransmitting the NG3 header only when the first downlink data (to whichreflective QoS is applied) is transmitted. Accordingly, although the UPfunction does not separately provide reflective QoS indication withrespect to subsequently generated/transmitted downlink data, the UE mayconsider that the reflective QoS continues to be applied (to a receiveddownlink packet) before the timer expires.

If the UP function transmits the reflective QoS indication and the timerto the UE again before the timer expires, the UE may reset the time thatoperates based on the reflective QoS indication and newly start thetimer. Through such a method, the UP function may increase the time whenreflective QoS is used/applied.

In another embodiment of the method 2, there may be a method for the UPfunction to include reflective QoS indication whenever it transmitsdownlink data in step 4 without using the timer. That is, the UE maygenerate a reflective QoS rule (a derived QoS rule in the case of thepresent embodiment) whenever it receives reflective QoS indication, andmay perform QoS marking on uplink data. In this case, if the UE does notreceive downlink data on which the reflective QoS indication is markedduring a specific time, the timer expires, and the UE may delete/removea corresponding rule.

In the case of the method 2, there is a problem in that the size of aheader is increased if a timer value is great because QoS markinginformation and timer information must be included in the header of adata packet, but there is an effect in that reflective QoS can beapplied even without the generation of additional (control) signaling.

In both the methods 1 and 2, if it is difficult to directly transmittimer information, the number of bits of a timer value can be reducedthrough a method of previously determining candidate timers to be usedin the process of producing a PDU session and transmitting the index ofa specific timer selected from the candidate timers. Specifically, ifthis method is applied to the method 2, a problem in that the size of aheader increases as a timer value increases can be solved. Table 2 belowillustrates timer values for reflective QoS which are exchanged in a PDUsession (setup) process.

TABLE 2 Timer index Timer value 1 T_1 (e.g., 1 min) 2 T_2 (e.g., 10 min)3 T_3 (e.g., 1 hour) . . . . . . N T_N (e.g., 1 day)

Alternatively, in the process of producing the PDU session, timerinformation to be used for reflective QoS may be previously negotiated,and the reflective QoS may be applied without the signaling/exchange ofadditional timer information. In this case, the timer information is notseparately transmitted, but a different value may not be used for eachrule (e.g., a derived QoS rule). In order to supplement this problem, ifa network node wants to use a timer value different from a timer valuedetermined while producing a PDU session, a method used in the method1/2 may be used. That is, in the method 1/2, if timer information forreflective QoS is not transmitted, a UE may use a timer valuedetermined/negotiated in the process of producing a PDU session. Iftimer information for reflective QoS is also transmitted, a UE may use atimer value indicated by the received timer information.

The method 2 may be summarized as follows.

Reflective QoS may be controlled for each packet using an RQI within theencapsulation header of the N3 reference point along with a QFI andreflective QoS timer (RQ timer) value. In this case, the reflective QoStimer value may be signaled to the UE or may be set as a default valuewhen the PDU session is established.

If the RQI is received by the (R)AN in a DL packet on the N3 referencepoint, the (R)AN may indicate that the QFI and corresponding DL packetare subjected to reflective QoS (i.e., a packet to which the reflectiveQoS is applied) with respect to the UE.

If the UE receives a DL packet subjected to reflective QoS:

-   -   If a derived QoS rule having a packet filter corresponding to a        DL packet is not present (i.e., if the same derived QoS rule has        not been previously stored), the UE may generate a new derived        QoS rule having a packet filter corresponding to a DL packet,        and start a timer (set to a RQ time value) for the newly        generated derived QoS rule.    -   Otherwise (i.e., if the same derived QoS rule has not been        previously stored), the UE may restart a timer associated with a        derived QoS rule that has been previously stored.

When the timer associated with the derived QoS rule expires, the UE maydelete the corresponding derived QoS rule.

In some embodiments, reflective QoS to which the timer has been appliedmay be controlled by the user plane or control plane as follows.

If reflective QoS is controlled by the user plane:

The reflective QoS may be controlled by the user plane for each packetusing an RQI within an encapsulation header within the N3 referencepoint along with a QFI and a reflective QoS timer (RQ timer). In thiscase, the RQ timer corresponds to the above timer, and may be set as adefault value or be signaled for the UE when a PDU session isestablished.

If 5GC determines to control reflective QoS through the user plane for aspecific SDF, the SMF may include indication in corresponding SDFinformation provided to the UPF through the N4 interface. With respectto a DL packet corresponding to the SDF, the UPF may set RQI bits withinan encapsulation header on the N3 reference point.

If a DL packet related to reflective QoS is received, the UE maygenerate a UE-derived QoS rule (i.e., a “derived QoS rule”) and may setthe timer as an RQ time value. If a UE-derived QoS rule having the samepacket filter is already present, the UE may restart a timercorresponding to the corresponding UE-derived QoS rule. Reflective QoSactivation through the user plane may be used to avoid out-of-bandsignaling (e.g., signaling over a non-3GPP access network).

If reflective QoS is controlled by the control plane:

The reflective QoS may be controlled by the control plane for each QoSflow. When the QoS flow is established, the UE may be provided with areflective QoS timer (RQ timer) specified for the QoS flow.

If 5GC determines to control reflective QoS through the control plane,the SMF may include RQA in a QoS flow parameter transmitted to the UEthrough the N1 interface.

When the UE receives a DL packet through a QoS flow in which the RQA hasbeen set as the RQI, the UE may generate a UE-derived QoS rule and starta timer set as an RQ time value. If a UE-derived QoS rule having thesame packet filter is already present, the UE may restart a timercorresponding to the corresponding UE-derived QoS rule.

When the timer associated with the UE-derived QoS rule expires, the UEmay delete/remove the corresponding UE-derived QoS rule.

The method 2 may have a problem in that reflective QoS-relatedinformation is also lost if a packet is lost in a data congestionsituation because the reflective QoS-related information is transmittedalong with data. Specifically, if the UPF transmits reflectiveQoS-related information only when it transmits the first downlink data,the UPF does not transmit additional reflective QoS-related informationuntil a timer expires. Accordingly, mismatching between the UPF and theUE is generated with respect to reflective QoS execution.

Accordingly, a procedure for recovering lost reflective QoS-relatedinformation is proposed below.

FIG. 18 is a flowchart illustrating a method of recovering reflectiveQoS-related information if the reflective QoS-related information islost while the method 2 is applied. In relation to this flowchart, thedescription of the flowchart of FIG. 17 may be appliedidentically/similarly, and a redundant description thereof is omitted.Specifically, steps 1 to 3 in this flowchart are the same as steps 1 to3 of FIG. 17, and a redundant description thereof is omitted.

4. The UP function has included the reflective QoS indication and thetimer in the NG3 header and transmitted the data, but the data may belost due to data congestion within the AN. Thereafter, the UP functionmay determine that all of pieces of reflective QoS-related information(e.g., QoS marking (e.g., QFI), reflective QoS indication (e.g., RQI)and/or the timer) have been successfully transmitted, and may transmitdata except the reflective QoS-related information.

5-6. The UE does not receive indication for reflective QoS and may notgenerate/apply a derived QoS rule. Instead, the UE may perform defaultQoS marking (apply a default QoS rule) on uplink data mapped to receiveddownlink data, and may transmit the uplink data. The UP function maydetect the QoS marking of the uplink data received from the UE, and mayrecognize that the QoS marking is not matched with its own reflectiveQoS (i.e., QoS marking). The UP function notifies the CP function ofthis mismatching. The CP function may recognize that it has indicatedreflective QoS in the UE based on its own QoS rule, and may instruct theUP function to indicate the reflective QoS again with respect to the UE.

7. The UP function may transmit reflective QoS-related information alongwith corresponding downlink data in response to a command from the CPfunction when downlink data mapped to reflective QoS (i.e., to which thereflective QoS is applied) is generated. In this case, the UP functionmay transmit the remaining time of the timer started upon timertransmission in step 4 to the UE or may reset the timer received fromthe CP function, may start the timer again, and may transmit it to theUE.

8. The UE may receive the reflective QoS-related information, maygenerate a reflective QoS rule (i.e., a derived QoS rule), and maytransmit uplink data (subjected to QoS marking) by applying thereflective QoS rule.

Uplink traffic may be a lot generated, but downlink traffic may berelatively rarely generated depending on the characteristics of anapplication. In this case, if reflective QoS is activated through inbandsignaling (a method of providing reflective QoS indication throughpacket marking), a situation in which a reflective QoS timer is notextended/reset may occur because there is no transmitted downlink packetif reflective QoS is applied based on the timer. That is, since uplinkpackets continue to be generated, a network wants to continue to use acorresponding derived QoS rule, but cannot extend the time during whicha reflective QoS rule is used unless a downlink packet is generateduntil a previously set timer value expires.

In this case, the network may transmit (indicate) an explicit QoS ruleor may transmit a reflective QoS rule (or reflective QoS-relatedinformation) with respect to the UE through control plane signaling.Furthermore, in order to stop a reflective QoS application, the networkmay reset or omit packet marking and transmit it. If a downlink packetthat may be transmitted is not present, however, the network cannotperform such an operation. Even in this case, the network maydelete/remove a reflective QoS rule (or derived QoS rule) throughcontrol plane signaling.

In summary, in a reflective QoS indication operation, if a network doesnot use inband signaling, this problem may be supplemented throughcontrol plane signaling (e.g., the method 1). In other words, uponreflective QoS execution, the network may optionally (complementarily)apply the inband signaling method or the control plane signaling methodaccording to a situation.

A new QoS framework for reflective QoS is hereinafter proposed.

A new wireless communication system (e.g., 5G) supports reflective QoSthrough an RAN under network control. The network may determine QoS tobe applied to DL traffic, and a UE may reflect UL traffic associatedwith the DL QoS. When the UE receives a DL packet to which reflectiveQoS must be applied, the UE may generate a new implicit QoS rule(alternatively a derived QoS rule) based on the DL packet. The packetfilter of the implicit QoS rule may be derived from the header of the DLpacket.

Reflective QoS indication may be signaled through the C-plane (i.e.,control signaling) (method 1) or may be signaled through inband (method2) or may be never signaled (method 3).

If control signaling is used, it does not comply with theobject/principle of reflective QoS to minimize signaling and mayincrease signaling. Inband signaling may be a better solution toreflective QoS because it does not introduce new signaling. In the caseof the last option (i.e., if signaling is not used), if a downlink flowis present, it means that reflective QoS is used in a downlink flow andall of corresponding uplink flows. In the case of this option, if anexplicit QoS rule is not provided, uplink QoS and downlink QoS may bealways the same.

In order to indicate reflective QoS, both the inband signaling methodand the non-signaling method may be used. The signaling method may bedetermined by a network during a PDU session establishment/setupprocedure. For example, if a UE is attached through 3GPP access, anetwork may use inband signaling for reflective QoS.

If the UE is attached through non-3GPP access, the network cannot useany signaling for reflective QoS.

A QoS framework according to a first embodiment may be determined indetail as follows:

1. A new wireless communication system (e.g., 5G) supports reflectiveQoS through an RAN under network control. The network may determine QoSto be applied to DL traffic, and a UE may reflect the DL QoS inassociated UL traffic. When the UE receives a DL packet to whichreflective QoS must be applied, it may generate a new implicit QoS rule(e.g., a derived QoS rule) based on the DL packet. The packet filter ofthe implicit QoS rule may be derived from the header of the DL packet.

Reflective QoS indication may be signaled through inband or may not besignaled in response to an instruction from the network. The indicationmethod may be determined by the network during a PDU sessionestablishment/setup procedure.

2. U-plane marking (i.e., the QoS marking) for QoS may be carried in anencapsulation header on NG3 (without a change of an e2e packet header).

3a. A default QoS rule and a pre-authorized QoS rule may be provided tothe UE when a PDU session is established/set up.

3b. The QoS rules may be provided to the RAN when the PDU session isestablished/set up using NG2 signaling (e.g., depending on an accesscapability).

4. QoS flow-specific QoS signaling through the C-plane may be necessaryfor a GBR SDF.

5. For the initialization, change or termination of an SDF not havingGBR requirements, QoS-related NG2 signaling corresponding to thepre-authorized QoS rule (other than PDU session establishment/setup)must be minimized.

6. For the initialization, change or termination of an SDF not havingGBR requirements, QoS-related NG1 signaling corresponding to thepre-authorized QoS rule (other than PDU session establishment/setup)must be minimized.

7. For a subscription and service distinction, the application of aservice data flow and UL rate restriction for each PDU session must beperformed in CN_UP.

CN_UP is an execution point reliable by a network and may process all ofpieces of traffic in a PDU session.

8. The AN may perform a rate restriction in the UL for each UE.

9. A QoS flow may be the finest granularity for QoS processing in an NGsystem.

10.1. In the downlink, the (R)AN may bind the QoS flow toaccess-specific resources based on corresponding QoS characteristicsprovided through NG3 marking and NG2 signaling. The packet filter is notused for binding between the access-specific resources and the QoS flowin the (R)AN.

10.2. The UE may bind uplink packets to the access-specific resourcesbased on information and/or a (derived) QoS rule (explicitly signaled orimplicitly derived by reflective QoS) for binding between theaccess-specific resources explicitly provided by an access network andthe uplink packets.

11. Some user plane marking may be a scalar value having a standardizedQoS characteristic.

12. Some user plane marking may be scalar values indicative of dynamicQoS parameters signaled through NG2.

13. The dynamic QoS parameters may include the followings:

a. Maximum flow bit rate

b. Guaranteed flow bit rate

c. Priority level

d. Packet delay budget

e. Packet error rate

f. Admission control

Hereinafter, there is proposed a solution for solving the followingthree issues proposed in relation to reflective QoS.

-   -   Issue 1: whether reflective QoS indication is signaled through        the C-plane or inband    -   Issue 2: whether a derived QoS rule (i.e., derived through        reflective QoS) has higher priority or lower priority than        signaled QoS rules    -   Issue 3: Whether reflective QoS can be applied to all of access        networks connected to the NG core

<Solution>

1. Reflective QoS Indication Method

A UE does not require an explicit QoS request message for reflective QoSbecause it drives an uplink QoS rule using the downlink QoS of acorresponding downlink flow. In order to maximize the advantages ofreflective QoS, there may be proposed an operation of indicatingreflective QoS using the inband signaling method. That is, inbandsignaling may be used for reflective QoS indication.

2. Valid Period of Derived QoS Rule

The valid period of a derived QoS rule generated through reflective QoSindication needs to be defined. If the derived QoS rule is valid while aPDU session is valid (or during the lifetime of the PDU session), toomany derived QoS rules are present in a UE, which may be a burden on theUE. Accordingly, the following two methods may be proposed in order toremove an unnecessary derived QoS rule.

One method is to use explicit signaling and the other method is to use atimer value. If explicit signaling is used, a network may delete/removea derived QoS rule using the explicit signaling whenever the networkwants. However, since there is a problem in that signaling is increased,this specification proposes that the lifetime of a derived QoS rule isrestricted using a timer value. Related detailed embodiments have beendescribed above in connection with FIGS. 16 to 18. The timer value maybe determined during a PDU session setup/establishment process.

That is, derived QoS through reflective QoS indication may have a validtimer determined during a PDU session setup/establishment procedure.

3. Priority of QoS Rules

If a derived QoS rule has higher priority than a signaled QoS rule, anetwork cannot apply the signaled QoS rule to the same flow until thetimer of the derived QoS rule expires. However, this is not preferredbecause the network must be able to update a QoS rule at any time.Accordingly, there may be proposed that a signaled QoS rule has thehighest priority and a default QoS rule has the lowest priority. Thatis, a derived QoS rule through reflective QoS indication may have lowerpriority than a signaled QoS rule, but may be set to have higherpriority than a default QoS rule.

4. Applicability of Reflective QoS to all of Access Networks

There is no reason to use reflective QoS only in a specific accessnetwork. Accordingly, reflective QoS may be used in all of accessnetworks.

A QoS framework according to a second embodiment in which theaforementioned solution has been reflected may be determined in detailas follows:

1a. A new wireless communication system (e.g., 5G) supports reflectiveQoS through the RAN under network control. The network may determine QoSto be applied to DL traffic, and a UE may reflect the DL QoS inassociated UL traffic. When the UE receives a DL packet to whichreflective QoS must be applied, it may generate a new derived QoS rulebased on the DL packet. The packet filter of the derived QoS rule may bederived from the DL packet (i.e., the header of the DL packet). In thecase of traffic subjected to reflective QoS, an UL packet may beQoS-processed in the same manner as the reflected DL packet (i.e.,having the same QFI or identically QoS-marked).

1b. Inband signaling may be used for reflective QoS indication.

1c. A derived QoS rule through reflective QoS indication may have avalid timer determined during a PDU session setup procedure.

1d. A signaled QoS rule may have the highest priority. The derived QoSrule through reflective QoS indication may have lower priority than thesignaled QoS rule, but may have higher priority than a default QoS rule.

1e. Reflective QoS may be used in a non-GBR service data flow.

2. U-plane marking (i.e., the QoS marking) for QoS may be carried in anencapsulation header on NG3 (without a change of an e2e packet header).

3a. A default QoS rule and a pre-authorized QoS rule may be provided toa UE when a PDU session is established/set up. The pre-authorized QoSrule corresponds to all of QoS rules provided when the PDU session isestablished/set up, and is different from the default QoS rule.

3b. The NAS-level QoS profile of a QoS rule provided in PDU sessionsetup for a UE must be also provided to the RAN using NG2 signaling whena PDU session is configured. The QoS rule may be provided to the NG ANwhen the PDU session is established/set up using NG2 signaling based onnon-3GPP access (e.g., depending on access performance).

3c. A QoS rule may include the QoS profile (A or B type) of anNAS-level, a packet filter and/or a precedence value.

3d. A signaled QoS rule may be provided to a UE connected through the NGRAN based on 3GPP access through NG1 signaling. In this case, it may beassumed that a UE that accesses a NextGen CN through non-3GPP accessuses a 3GPP NAS signal.

4. A GBR SDF may be supported in the NextGen system and may require theQoS flow-specific QoS signaling through the C-plane.

5. For the initialization, change or termination of an SDF not havingGBR requirements, QoS-related NG2 signaling corresponding to apre-authorized QoS rule (other than PDU session establishment/setup)must be minimized.

6. For the initialization, change or termination of an SDF not havingGBR requirements, QoS-related NG1 signaling corresponding to apre-authorized QoS rule (other than PDU session establishment/setup)must be minimized.

7a. For a subscription and service distinction, a maximum bit raterestriction of a service data flow (SDF) per UL and DL must be performedin CN_UP, and the CN_UP corresponds to an execution point reliable to anetwork. Rate restriction execution per PDU session may be applied to aflow that does not require a guaranteed flow bit rate.

7b. In the case of a flow that does not require a guaranteed flow bitrate, a maximum bit rate (MBR) restriction of UL and DL per PDU sessionmay be applied to the CN_UP. In the case of a multi-homed PDU session, aPDU session MBR may be applied to each UPF that terminates the NG6interface. This may be executed for each UPF. An AMBR for each DN namemay not be supported.

8. The AN must execute a maximum bit rate restriction per UE on a flowthat does not require a guaranteed flow bit rate in the UL and DL.

9. A QoS flow may be the finest granularity for QoS processing in the NGsystem. User plane traffic having the same NG3 marking value within aPUD session corresponds to the QoS flow.

10.1.1. In the downlink, the (R)AN may bind the QoS flow toaccess-specific resources based on corresponding QoS characteristicsprovided through NG3 marking and NG2 signaling by considering an NG3tunnel associated with a downlink packet. A packet filter is not used tobind the QoS flows to the access-specific resources in the (R)AN.

10.1.2. When an UL packet passes through from the (R)AN to the CN, theRAN may determine NG3 QoS marking and select an NG3 tunnel based oninformation received from an access stratum.

10.2.1. In a higher layer, a UE may match the uplink packet to the QoSrule and bind the uplink packet to the NAS-level QoS profile (A- orB-type) of the QoS rule (explicitly signaled or implicitly derived fromreflective QoS).

10.2.2. When the UL packet passes through the AS in the higher layer ofthe UE, the higher layer may indicate the NAS-level QoS profile (throughcorresponding QoS marking) in the AS by including information thatenables the AS to identify a PDU session.

10.2.3. Inversely, when the DL packet passes through from the AS to aproper higher layer instance of the UE, to select a proper higher layerinstance corresponding to a PDU session is a responsibility for the AS.The AS may also indicate the NAS-level QoS profile (throughcorresponding QoS marking) in the higher layer instance.

In the case of 10.2.2. and 10.2.3., there is no precondition for thenecessity of U-plane marking from the RAN to the UE.

In order to indicate QoS requested in the 10.2.4. IP packet, in the caseof a QoS application using a DSCP, a packet filter including DSCPmarking within a QoS rule provided by CN_CP may be used for binding withspecific QoS marking.

10.3. If the RAN has determined that flexible mapping (e.g., other thanone-to-one) is present between an NAS-level QoS profile and an AS-levelQoS, this mapping is transparent to a higher layer and does not have aninfluence on NG3 marking. It is assumed that an access stratum complieswith QoS characteristics associated with the NAS-level QoS profile.

A method of defining the AS-level QoS of a DRB and mapping an uplink anddownlink packet (having an associated QoS profile and associated PDUsession information) to a DRB depends on the RAN.

11. Some user plane QoS marking is a scalar value having standardizedQoS characteristics (referred to as an A-type QoS profile).

12. Some user plane QoS marking is a scalar value indicative of dynamicQoS parameters signaled through NG2 (referred to as a B-type QoSprofile).

The QoS marking value indicates the type (A- or B-type) of associatedQoS profile.

13. The QoS parameters may include the followings:

a. Maximum flow bit rate

b. Guaranteed flow bit rate

c. Priority level

d. Packet delay budget

e. Packet error rate

f. Admission control

The parameters c, d and e are applied to 11. and 12. only, and theparameters a, b and f are applied to 12. only.

14. A QoS framework does not assume the necessity of an NG3 tunnel foreach QoS flow.

15. With respect to not-guaranteed bit rate QoS flows corresponding topre-authorized QoS rules, a UE may transmit UL traffic without specificadditional NG1 signaling.

16. UE-triggered QoS establishment for a guaranteed bit rate QoS flow isbased on explicit UE-request QoS through NG1.

Hereinafter, there is proposed the deactivation mechanism of a derivedQoS rule based on a timer set while a PDU session is established.

There are some candidate solutions for the deactivation of a derived QoSrule.

A first solution is to use implicit deactivation without signaling or apre-configuration (i.e., this is left as an implementation of a UE and5G-CN). Accordingly, in the case of this solution, a deactivationprocess does not need to be separately standardized. However, in orderto support uplink QoS verification, a 5G CN and a UE need to have thesame QoS rule. Accordingly, implicit deactivation cannot be used becauseit does not guarantee a QoS rule synchronized between the 5G CN and theUE.

A second solution is to use explicit signaling in order to deactivate aderived QoS rule. If reflective QoS is activated through control planesignaling, this solution may be used. However, if reflective QoS isactivated through user plane marking, this solution is inappropriatebecause to avoid out-of-band signaling is the key point of user planeactivation.

A third solution is a method similar to a method supported in the EPS.In the EPS, a UE reflective QoS procedure may be deleted as follows (TS24.139).

In the EPS, a UE may generate a table when it transmits/receives acorresponding packet and manage an updated time stamp. The time when theentry is maintained depends on a UE implementation.

A similar mechanism may be used in the 5G system. If a network indicatesreflective QoS activation, the network may start a timer with a presetvalue determined during PDU session setup. When a UE receives reflectiveQoS indication, it may start (or restart/reset) the same timer. When thetimer expires, a derived QoS rule may be deactivated.

That is, if an UPF indicates the activation of reflective QoS, the UPFmay start a deactivation timer previously set during PDU session setup.Whenever the UPF indicates the reflective QoS, the UPF may reset thetimer. If reflective QoS indication is received, the UE may also startthe deactivation timer and may reset the timer whenever it receivesreflective QoS indication. The derived QoS rule is deactivated when thetimer expires.

In addition to the aforementioned methods, other some methods fordeactivating reflective QoS may be present. User plane solutions thatdeactivate reflective QoS by basically not including an RQI or basicallyincluding reflective QoS deactivation indication (RQDI) correspond tothe some methods. However, if there is no downlink packet associatedwith reflective QoS, such a mechanism cannot be executed. In order todeactivate the reflective QoS, control plane signaling is required.

In contrast, the deactivation method using a timer proposed by thisspecification has an advantage in that it does not require additionalsignaling for deactivating reflective QoS.

Such a concept of this specification is a concept corresponding to themethod 2 and may be summarized in brief as follows and may be reflectedin TS 23.501.

1. Inactivation of Reflective QoS

1-1. General

5GC supports reflective QoS deactivation. Reflective QoS may bedeactivated through the user plane and the control plane. 5GC maydetermine whether a reflective QoS function will be deactivated throughthe control plane or deactivated through the user plane based on apolicy and access type.

1-2. Reflective QoS Deactivation Through User Plane

In the establishment process of a PDU session, the SMF may notify a UEof a deactivation timer value. If the UPF indicates reflective QoS, theSMF may configure a deactivation timer so that the time starts. The UEmay also start the deactivation timer whenever it receives reflectiveQoS indication. The UPF may reset the (corresponding) timer when itincludes an RQI in an encapsulation header on the N3 reference point.The UE may reset the (corresponding) timer whenever it receivesreflective QoS indication.

If 5GC has determined to deactivate a reflective QoS function throughthe U-plane, the SMF may transmit a QoS rule having user planereflective QoS deactivation indication to the UPF. In this case, if adownlink packet corresponding to the reflective QoS is present, the UPFmay stop the indication of an RQI within an encapsulation header.Furthermore, the UE does not reset an associated deactivation timer whenit receives a packet not having an RQI. The UE and UPF may remove aderived QoS rule when the deactivation timer expires.

1-3. Reflective QoS Deactivation Through Control Plane

If 5GC has determined to deactivate reflective QoS through the controlplane, the SMF may explicitly transmit a deactivation request (e.g.,transmits an updated QoS rule or transmits a reflective QoS rule removalcommand) to the UE and UPF. If the SMF has updated the QoS rule, the UEand UPF may remove a derived QoS rule generated by the updated QoS rule.

FIG. 19 is a flowchart illustrating a reflective QoS procedure accordingto an embodiment of the present invention. The description described inrelation to FIGS. 15 to 18 may be applied to this flowchartidentically/similarly, and a redundant description thereof is omitted.

First, a UE may receive a downlink packet from a network (S1910). Inthis case, the downlink packet may correspond to a packet in which theapplication of reflective QoS has been indicated. More specifically, thedownlink packet may correspond to a packet to which reflective QoSapplication has been indicated by a reflective QoS indicator. In thiscase, a network may correspond to the AN that receives reflective QoSindication indicative of the reflective QoS application of the downlinkpacket and QoS marking through an encapsulation header on the N3reference point from a user plane function.

Next, the UE may derive a QoS rule based on the downlink packet (S1920).More specifically, the UE may check whether a QoS rule associated withthe downlink packet is present. If a QoS rule associated with thedownlink packet is not present, the UE may derive a QoS rule based onthe downlink packet and start a timer. If a QoS rule associated with thedownlink packet is present, the UE may perform steps S1930 and S1940below.

Next, the UE may transmit an uplink packet to the network by applyingthe QoS marking of the downlink packet to the uplink packet using the(newly generated or existing) QoS rule (S1930). More specifically, theUE may filter an uplink packet matched with a packet filter included inthe QoS rule by evaluating a plurality of uplink packets in order ofprecedence values. Furthermore, the UE may transmit the filtered uplinkpacket to the network by applying QoS marking included in the QoS ruleto the filtered uplink packet. In this case, applying the QoS markingmay mean marking a QFI (or binding with a specific QoS flow). The QoSmarking may correspond to the ID of a QoS flow within the downlinkpacket (or QoS rule).

Next, when the UE receives a downlink packet before a timer associatedwith the QoS rule expires, it may restart the corresponding timer(S1940). When the UE receives the downlink packet after the timerexpires, the UE may newly start the corresponding timer. When the timerexpires, the UE deletes the derived QoS rule. The value of the timer maybe previously determined in the PDU session establishment procedure ofthe UE.

The QoS rule may be used to determine a mapping relation between theuplink packet and the QoS flow. The QoS rule may include a packet filterderived from the downlink packet (specifically, the header of thedownlink packet), the QoS marking of the downlink packet and aprecedence value used to determine the evaluation order of the uplinkpacket.

The QoS rule derived according to such reflective QoS execution may havelower priority than an explicitly signaled QoS rule. Furthermore, theapplication of such a reflective QoS may be deactivated through a userplane or a control plane.

General Apparatus to which the Present Invention May be Applied

FIG. 20 shows a block diagram of a communication apparatus according toan embodiment of the present invention.

Referring to FIG. 20, a wireless communication system includes a networknode 2010 and a plurality of UEs 2020. The apparatus shown in thisdrawing may be implemented to perform at least one of the aforementionednetwork/UE functions and may be implemented to integrate and perform oneor more of the functions.

The network node 2010 includes a processor 2011, memory 2012, and acommunication module 2013.

The processor 2011 implements at least one function, process and/ormethod proposed in FIGS. 1 to 19 and/or the function, process and/ormethod proposed in this document. Furthermore, a module, program, etc.that implements the function, process and/or method proposed in thisspecification may be stored in the memory 2012 and executed by theprocessor 2011.

The layers of a wired/wireless interface protocol may be implemented bythe processor 2011. Furthermore, the processor 2011 may be implementedto independently apply the contents described in the various embodimentsproposed in this document or to apply two or more of the embodiments atthe same time.

The memory 2012 is connected to the processor 2011 and stores varioustypes of information for driving the processor 2011. The memory 2012 maybe located inside or outside the processor 2011 and may be connected tothe processor 2011 by well-known various means.

The communication module 2013 is connected to the processor 2011 andtransmits and/or receives wired/wireless signals. The network node 2010may include, for example, an eNB, an MME, an HSS, an SGW, a PGW, anSCEF, an SCS/AS, an AUSF, an AMF, a PCF, an SMF, a UDM, a UPF, an AF, an(R)AN, a UE, an NEF, an NRF, a UDSF and/or an SDSF. Specifically, if thenetwork node 2010 is an eNB (or if it is implemented to perform an (R)ANfunction), the communication module 2013 may include a radio frequency(RF) unit for transmitting/receiving radio signals. In this case, thenetwork node 2010 may have a single antenna or multiple antennas.

The UE 2020 includes a processor 2021, memory 2022 and a communicationmodule (or RF unit) 2023. The processor 2021 implements at least onefunction, process and/or method proposed in FIGS. 1 to 19 and/or thefunction, process and/or method proposed in this document. Furthermore,a module, program, etc. that implements the function, process and/ormethod proposed in this specification may be stored in the memory andexecuted by the processor 2021.

The layers of a wired/wireless interface protocol may be implemented bythe processor 2021. Furthermore, the processor 2021 may be implementedto independently apply the contents described in the various embodimentsproposed in this document or to apply two or more of the embodiments atthe same time.

The memory 2022 is connected to the processor 2021 and stores varioustypes of information for driving the processor 2021. The memory 2022 maybe located inside or outside the processor 2021 and may be connected tothe processor 2021 by well-known various means

The memory 2012, 2022 may be located inside or outside the processor2011, 2021 and may be connected to the processor 2011, 2021 bywell-known various means. Furthermore, the network node 2010 (if it isan eNB) and/or the UE 2020 may have a single antenna or multipleantennas.

FIG. 21 shows a block diagram of a communication apparatus according toan embodiment of the present invention.

Specifically, FIG. 21 is a more detailed diagram of the UE of FIG. 20.

Referring to FIG. 21, the UE may include a processor (or digital signalprocessor (DSP)) 2110, an RF module (or RF unit) 2135, a powermanagement module 2105, an antenna 2140, a battery 2155, a display 2115,a keypad 2120, memory 2130, a subscriber identification module (SIM)card 2125 (this element is optional), a speaker 2145 and a microphone2150. The UE may also include a single antenna or multiple antennas.

The processor 2110 implements the functions, processes and/or methodsproposed in FIGS. 1 to 20. The layers of a radio interface protocol maybe implemented by the processor 2110.

The memory 2130 is connected to the processor 2110 and storesinformation related to the operation of the processor 2110. The memory2130 may be located inside or outside the processor 2110 and may beconnected to the processor 2110 by well-known various means.

A user inputs command information, such as a telephone number, bypressing (or touching) a button of the keypad 2120 or by voiceactivation using the microphone 2150, for example. The processor 2110processes a proper function, such as receiving such command informationor making a call to a telephone number, so that the function isperformed. Operational data may be extracted from the SIM card 2125 orthe memory 2130. Furthermore, the processor 2110 may display commandinformation or driving information on the display 2115 so that a usercan recognize the information or for convenience.

The RF module 2135 is connected to the processor 2110 and transmitsand/or receives RF signals. The processor 2110 transfers commandinformation to the RF module 2135 so that a radio signal forming voicecommunication data, for example, is transmitted in order to initiatecommunication. The RF module 2135 includes a receiver and a transmitterin order to transmit and receive radio signals. The antenna 2140functions to transmit and receive radio signals. When the RF module 2135receives a radio signal, it transfers the signal for the processing ofthe processor 2110 and may convert the signal into a baseband. Theprocessed signal may be converted into audible or readable informationthrough the speaker 2145.

In the aforementioned embodiments, the elements and characteristics ofthe present invention have been combined in specific forms. Each of theelements or characteristics may be considered to be optional unlessotherwise described explicitly. Each of the elements or characteristicsmay be implemented in a form to be not combined with other elements orcharacteristics. Furthermore, some of the elements and/or thecharacteristics may be combined to form an embodiment of the presentinvention. Order of the operations described in the embodiments of thepresent invention may be changed. Some of the elements orcharacteristics of an embodiment may be included in another embodimentor may be replaced with corresponding elements or characteristics ofanother embodiment. It is evident that an embodiment may be constructedby combining claims not having an explicit citation relation in theclaims or may be included as a new claim by amendments after filing anapplication.

The embodiment according to the present invention may be implemented byvarious means, for example, hardware, firmware, software or acombination of them. In the case of an implementation by hardware, theembodiment of the present invention may be implemented using one or moreapplication-specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In the case of an implementation by firmware or software, the embodimentof the present invention may be implemented in the form of a module,procedure or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be located inside or outside the processor andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention has been described based on an example in which ithas been applied to the 3GPP LTE/LTE-A/5G (NextGen) systems, but may beapplied to various wireless communication systems in addition to the3GPP LTE/LTE-A/5G (NextGen) systems.

The invention claimed is:
 1. A method for a user equipment (UE) toperform reflective quality of service (QoS) in a wireless communicationsystem, the method comprising steps of: receiving a downlink packet froma network, wherein the downlink packet is a packet to which anapplication of the reflective QoS is indicated; deriving a QoS rulebased on the downlink packet; applying a QoS marking of the downlinkpacket to an uplink packet using the QoS rule and transmitting theuplink packet to the network; and restarting a timer associated with theQoS rule when the downlink packet is received before the timer expires.2. The method of claim 1, further comprising a step of deleting the QoSrule when the timer expires.
 3. The method of claim 2, furthercomprising a step of starting the timer when the downlink packet isreceived after the timer expires.
 4. The method of claim 2, wherein avalue of the timer is previously determined in a protocol data unit(PDU) session establishment procedure of the UE.
 5. The method of claim2, wherein, when the network is an access network (AN), the AN is anetwork node receiving reflective QoS indication indicative of thereflective QoS application of the downlink packet and the QoS markingthrough an encapsulation header on an N3 reference point from a userplane function.
 6. The method of claim 2, wherein the QoS markingcorresponds to an identifier of a QoS flow of the downlink packet. 7.The method of claim 6, wherein the QoS rule is used to determine amapping relation between the uplink packet and the QoS flow.
 8. Themethod of claim 7, wherein the QoS rule comprises a packet filterderived from the downlink packet, the QoS marking of the downlinkpacket, and a precedence value used to determine an evaluation order ofthe uplink packet.
 9. The method of claim 8, wherein the packet filteris derived from a header of the downlink packet.
 10. The method of claim8, wherein the step of applying the QoS marking of the downlink packetto the uplink packet using the QoS rule and transmitting the uplinkpacket to the network comprises steps of: filtering an uplink packetmatched with the packet filter included in the QoS rule by evaluating aplurality of uplink packets in the order of the precedence value; andapplying the QoS marking included in the QoS rule to the filtered uplinkpacket and transmitting the filtered uplink packet to the network. 11.The method of claim 2, wherein the step of deriving the QoS rule basedon the downlink packet comprises steps of: checking whether the QoS ruleassociated with the downlink packet is present; and deriving the QoSrule based on the downlink packet if the QoS rule associated with thedownlink packet is not present and starting the timer.
 12. The method ofclaim 2, wherein the QoS rule derived according to the reflective QoSapplication has lower priority than an explicitly signaled QoS rule. 13.The method of claim 2, wherein the application of the reflective QoS isdeactivated through a user plane or a control plane.
 14. A userequipment (UE) for performing reflective quality of service (QoS) in awireless communication system, the UE comprising: a communication moduleconfigured to transmit/receive a signal; and a processor configured tocontrol the communication module, wherein the processor is furtherconfigured to: receive a downlink packet from a network, the downlinkpacket being a packet to which an application of the reflective QoS isindicated, derive a QoS rule based on the downlink packet, apply a QoSmarking of the downlink packet to an uplink packet using the QoS ruleand transmit the uplink packet to the network, and restart a timerassociated with the QoS rule when the downlink packet is received beforethe timer expires.
 15. The UE of claim 14, wherein the processor isfurther configured to delete the QoS rule when the timer expires.